@article {zhu2023hubbardnet,
	title = {HubbardNet: Efficient predictions of the Bose-Hubbard model spectrum with deep neural networks},
	journal = {Physical Review Research},
	volume = {5},
	number = {4},
	year = {2023},
	pages = {043084},
	publisher = {APS},
	doi = {10.1103/PhysRevResearch.5.043084},
	author = {Zhu, Ziyan and Marios Mattheakis and Weiwei Pan and Efthimios Kaxiras}
}
@article {bennett2023twisted,
	title = {Twisted bilayer graphene revisited: minimal two-band model for low-energy bands},
	journal = {arXiv preprint arXiv:2310.12308},
	year = {2023},
	doi = {10.48550/arXiv.2310.12308},
	author = {Bennett, Daniel and Larson, Daniel T and Sharma, Louis and Carr, Stephen and Efthimios Kaxiras}
}
@article {nessralla2023modulating,
	title = {Modulating the Electrochemical Intercalation of Graphene Interfaces with α-RuCl3 as a Solid-State Electron Acceptor},
	journal = {Nano Letters},
	year = {2023},
	publisher = {ACS Publications},
	doi = {10.1021/acs.nanolett.3c02877},
	author = {Nessralla, Jonathon and Larson, Daniel T and Takashi Taniguchi and Kenji Watanabe and Efthimios Kaxiras and Bediako, D Kwabena}
}
@article {schleder2023one,
	title = {One-Dimensional Moir{\'e} Physics and Chemistry in Heterostrained Bilayer Graphene},
	journal = {arXiv preprint arXiv:2306.09799},
	year = {2023},
	doi = {10.1021/acs.jpclett.3c01919},
	author = {Schleder, Gabriel R and Pizzochero, Michele and Efthimios Kaxiras}
}
@article {rhone2023artificial,
	title = {Artificial Intelligence Guided Studies of van der Waals Magnets},
	journal = {Advanced Theory and Simulations},
	year = {2023},
	pages = {2300019},
	publisher = {Wiley Online Library},
	doi = {https://doi.org/10.1002/adts.202300019},
	author = {Trevor David Rhone and Romakanta Bhattarai and Haralambos Gavras and Bethany Lusch and Misha Salim and Marios Mattheakis and Larson, Daniel T and Yoshiharu Krockenberger and Efthimios Kaxiras}
}
@article {tepliakov2023dirac,
	title = {Dirac half-semimetallicity and antiferromagnetism in graphene nanoribbon/hexagonal boron nitride heterojunctions},
	journal = {arXiv preprint arXiv:2305.15214},
	year = {2023},
	doi = {https://doi.org/10.48550/arXiv.2305.09531},
	author = {Tepliakov, Nikita V and Ma, Ruize and Lischner, Johannes and Efthimios Kaxiras and Mostofi, Arash A and Pizzochero, Michele}
}
@article {zheng2023electronic,
	title = {Electronic ratchet effect in a moir{\'e} system: signatures of excitonic ferroelectricity},
	journal = {arXiv preprint arXiv:2306.03922},
	year = {2023},
	author = {Zheng, Zhiren and Wang, Xueqiao and Zhu, Ziyan and Carr, Stephen and Devakul, Trithep and de la Barrera, Sergio and Paul, Nisarga and Huang, Zumeng and Gao, Anyuan and Zhang, Yang and others}
}
@article {ghorashi2023highly,
	title = {Highly-confined and tunable plasmonics based on two-dimensional solid-state defect lattices},
	journal = {arXiv preprint arXiv:2305.01173},
	year = {2023},
	doi = {https://doi.org/10.48550/arXiv.2305.01173},
	author = {Ghorashi, Ali and Nicholas Rivera and Bowen Shi and Sundararaman, Ravishankar and Efthimios Kaxiras and John Joannopoulos and Marin Soljacic}
}
@article {papamokos2023evict,
	title = {How to evict HP1 from H3: Using a complex salt bridge},
	journal = {Biophysical Chemistry},
	year = {2023},
	pages = {107062},
	publisher = {Elsevier},
	doi = {https://doi.org/10.1016/j.bpc.2023.107062},
	author = {George V. Papamokos and Efthimios Kaxiras}
}
@article {ko2023operando,
	title = {Operando electron microscopy investigation of polar domain dynamics in twisted van der Waals homobilayers},
	journal = {Nature Materials},
	year = {2023},
	pages = {1{\textendash}7},
	publisher = {Nature Publishing Group UK London},
	doi = {https://doi.org/10.1038/s41563-023-01595-0},
	author = {Ko, Kahyun and Yuk, Ayoung and Rebecca Engelke and Carr, Stephen and Kim, Junhyung and Park, Daesung and Heo, Hoseok and Kim, Hyun-Mi and Kim, Seul-Gi and Kim, Hyeongkeun and others}
}
@article {puntel2023photoinduced,
	title = {Photoinduced dynamics of flat bands in the kagome metal CoSn},
	journal = {arXiv preprint arXiv:2305.09531},
	year = {2023},
	doi = {https://doi.org/10.48550/arXiv.2305.09531},
	author = {Puntel, Denny and Bronsch, Wibke and Tuniz, Manuel and Kang, Mingu and Neves, Paul M and Fang, Shiang and Efthimios Kaxiras and Checkelsky, Joseph G and Comin, Riccardo and Parmigiani, Fulvio and others}
}
@article {morales2023pressure,
	title = {Pressure{\textendash}enhanced fractional Chern insulators in moir{\'e} transition metal dichalcogenides along a magic line},
	journal = {arXiv preprint arXiv:2304.06669},
	year = {2023},
	doi = {https://doi.org/10.48550/arXiv.2304.06669},
	author = {Morales-Dur{\'a}n, Nicol{\'a}s and Jie Wang and Schleder, Gabriel R and Angeli, Mattia and Zhu, Ziyan and Efthimios Kaxiras and Repellin, C{\'e}cile and Cano, Jennifer}
}
@article {bennett2023theory,
	title = {Theory of polarization textures in crystal supercells},
	journal = {arXiv preprint arXiv:2305.01404},
	year = {2023},
	doi = {https://doi.org/10.48550/arXiv.2305.01404},
	author = {Bennett, Daniel and Jankowski, Wojciech J and Chaudhary, Gaurav and Efthimios Kaxiras and Robert-Jan Slager}
}
@article {engelke2023topological,
	title = {Topological nature of dislocation networks in two-dimensional moir{\'e} materials},
	journal = {Physical Review B},
	volume = {107},
	number = {12},
	year = {2023},
	pages = {125413},
	publisher = {APS},
	doi = {https://doi.org/10.1103/PhysRevB.107.125413},
	author = {Rebecca Engelke and Yoo, Hyobin and Carr, Stephen and Xu, Kevin and Cazeaux, Paul and Allen, Richard and Valdivia, Andres Mier and Luskin, Mitchell and Efthimios Kaxiras and Kim, Minhyong and others}
}
@article {babar2023twisto,
	title = {Twisto-electrochemical activity volcanoes in Trilayer Graphene},
	journal = {arXiv preprint arXiv:2306.00028},
	year = {2023},
	author = {Babar, Mohammad and Zhu, Ziyan and Kurchin, Rachel and Efthimios Kaxiras and Viswanathan, Venkatasubramanian}
}
@article {chaves2023semiclassical,
	title = {Semiclassical Electron and Phonon Transport from First Principles: Application to Layered Thermoelectrics},
	journal = {Journal of Computational Electronics},
	year = {2023},
	doi = {10.48550/arXiv.2302.00202},
	url = {https://doi.org/10.1007/s10825-023-02062-4},
	author = {Chaves, Anderson S and Pizzochero, Michele and Larson, Daniel T and Antonelli, Alex and Efthimios Kaxiras}
}
@article {tepliakov2023unveiling,
	title = {Unveiling and Manipulating Hidden Symmetries in Graphene Nanoribbons},
	journal = {Physical Review Letters},
	volume = {130},
	number = {2},
	year = {2023},
	pages = {026401},
	publisher = {APS},
	doi = {10.1103/PhysRevLett.130.026401},
	author = {Tepliakov, Nikita V and Lischner, Johannes and Efthimios Kaxiras and Mostofi, Arash A and Pizzochero, Michele}
}
@article {zhu2022electric,
	title = {Electric field tunable layer polarization in graphene/boron-nitride twisted quadrilayer superlattices},
	journal = {Physical Review B},
	volume = {106},
	number = {20},
	year = {2022},
	pages = {205134},
	publisher = {APS},
	doi = {10.1103/PhysRevB.106.205134},
	author = {Zhu, Ziyan and Carr, Stephen and Qiong Ma and Efthimios Kaxiras}
}
@article {zhang2022gate,
	title = {Gate-tunable Veselago interference in a bipolar graphene microcavity},
	journal = {Nature communications},
	volume = {13},
	number = {1},
	year = {2022},
	pages = {6711},
	publisher = {Nature Publishing Group UK London},
	doi = {10.1038/s41467-022-34347-w},
	author = {Zhang, Xi and Wei Ren and Bell, Elliot and Zhu, Ziyan and Tsai, Kan-Ting and Luo, Yujie and Kenji Watanabe and Takashi Taniguchi and Efthimios Kaxiras and Luskin, Mitchell and others}
}
@article {mattheakis2022first,
	title = {First principles physics-informed neural network for quantum wavefunctions and eigenvalue surfaces},
	journal = {arXiv preprint arXiv:2211.04607},
	year = {2022},
	doi = {10.48550/arXiv.2211.04607},
	author = {Marios Mattheakis and Schleder, Gabriel R and Larson, Daniel and Efthimios Kaxiras}
}
@article {cho2022modulation,
	title = {Modulation Doping of Single-Layer Semiconductors for Improved Contact at Metal Interfaces},
	journal = {Nano Letters},
	volume = {22},
	number = {23},
	year = {2022},
	pages = {9700{\textendash}9706},
	publisher = {ACS Publications},
	doi = {10.1021/acs.nanolett.2c04011},
	author = {Cho, Yeonchoo and Schleder, Gabriel R and Larson, Daniel T and Brutschea, Elise and Byun, Kyung-Eun and Park, Hongkun and Philip Kim and Efthimios Kaxiras}
}
@article {angeli2022twistronics,
	title = {Twistronics of Janus transition metal dichalcogenide bilayers},
	journal = {Physical Review B},
	volume = {106},
	number = {23},
	year = {2022},
	pages = {235159},
	publisher = {APS},
	doi = {10.1103/PhysRevB.106.235159},
	author = {Angeli, Mattia and Schleder, Gabriel R and Efthimios Kaxiras}
}
@article {hsieh2022domain,
	title = {Domain-dependent surface adhesion in twisted few-layer graphene: Platform for moir{\'e}-assisted chemistry},
	journal = {Nano Letters},
	volume = {23},
	number = {8},
	year = {2022},
	pages = {3137-3143},
	abstract = {Twisted van der Waals multilayers are widely regarded as a rich platform to access novel electronic phases thanks to the multiple degrees of freedom available for controlling their electronic and chemical properties. Here, we propose that the stacking domains that form naturally due to the relative twist between successive layers act as an additional {\textquotedblright}knob{\textquotedblright} for controlling the behavior of these systems and report the emergence and engineering of stacking domain-dependent surface chemistry in twisted few-layer graphene. Using mid-infrared near-field optical microscopy and atomic force microscopy, we observe a selective adhesion of metallic nanoparticles and liquid water at the domains with rhombohedral stacking configurations of minimally twisted double bi- and trilayer graphene. Furthermore, we demonstrate that the manipulation of nanoparticles located at certain stacking domains can locally reconfigure the moir{\'e} superlattice in their vicinity at the micrometer scale. Our findings establish a new approach to controlling moir{\'e}-assisted chemistry and nanoengineering.},
	doi = {10.48550/arXiv.2210.10843},
	url = {https://doi-org.ezp-prod1.hul.harvard.edu/10.1021/acs.nanolett.2c04137},
	author = {Hsieh, Valerie and Halbertal, Dorri and Finney, Nathan R and Zhu, Ziyan and Gerber, Eli and Pizzochero, Michele and Kucukbenli, Emine and Schleder, Gabriel R and Angeli, Mattia and Kenji Watanabe and others}
}
@article {lu2022low,
	title = {Low-energy moir{\'e} phonons in twisted bilayer van der Waals heterostructures},
	journal = {Physical Review B},
	volume = {106},
	number = {14},
	year = {2022},
	pages = {144305},
	publisher = {APS},
	doi = {10.1103/PhysRevB.106.144305},
	author = {Lu, Jonathan Z and Zhu, Ziyan and Angeli, Mattia and Larson, Daniel T and Efthimios Kaxiras}
}
@article {chaves2022out,
	title = {Out-of-plane thermoelectric performance for p-doped GeSe},
	journal = {Physical Review B},
	volume = {105},
	number = {20},
	year = {2022},
	pages = {205201},
	publisher = {APS},
	doi = {10.1103/PhysRevB.105.205201},
	author = {Chaves, Anderson S and Larson, Daniel T and Efthimios Kaxiras and Antonelli, Alex}
}
@article {angeli2022modeling,
	title = {Modeling the effect of the vaccination campaign on the COVID-19 pandemic},
	journal = {Chaos, Solitons \& Fractals},
	volume = {154},
	year = {2022},
	pages = {111621},
	publisher = {Elsevier},
	doi = {10.1016/j.chaos.2021.111621},
	author = {Angeli, Mattia and Georgios Neofotistos and Marios Mattheakis and Efthimios Kaxiras}
}
@article {turkel2022orderly,
	title = {Orderly disorder in magic-angle twisted trilayer graphene},
	journal = {Science},
	volume = {376},
	number = {6589},
	year = {2022},
	pages = {193{\textendash}199},
	publisher = {American Association for the Advancement of Science},
	doi = {10.1126/science.abk1895},
	author = {Turkel, Simon and Swann, Joshua and Zhu, Ziyan and Maine Christos and K. Watanabe and T. Taniguchi and Sachdev, Subir and Mathias S Scheurer and Efthimios Kaxiras and Dean, Cory R and others}
}
@article {li2021development,
	title = {Development of robust neural-network interatomic potential for molten salt},
	journal = {Cell Reports Physical Science},
	volume = {2},
	number = {3},
	year = {2021},
	publisher = {Elsevier},
	doi = {10.1016/j.xcrp.2021.100359},
	author = {Li, Qing-Jie and K{\"u}{\c c}{\"u}kbenli, Emine and Lam, Stephen and Khaykovich, Boris and Efthimios Kaxiras and Li, Ju}
}
@article {shaidu2021systematic,
	title = {A systematic approach to generating accurate neural network potentials: The case of carbon},
	journal = {npj Computational Materials},
	volume = {7},
	number = {1},
	year = {2021},
	pages = {52},
	publisher = {Nature Publishing Group UK London},
	doi = {10.1038/s41524-021-00508-6},
	author = {Shaidu, Yusuf and K{\"u}{\c c}{\"u}kbenli, Emine and Lot, Ruggero and Pellegrini, Franco and Efthimios Kaxiras and de Gironcoli, Stefano}
}
@article {halbertal2021moire,
	title = {Moir{\'e} metrology of energy landscapes in van der Waals heterostructures},
	journal = {Nature communications},
	volume = {12},
	number = {1},
	year = {2021},
	pages = {1{\textendash}8},
	publisher = {Nature Publishing Group},
	doi = {10.1038/s41467-020-20428-1},
	author = {Halbertal, Dorri and Finney, Nathan R and Sunku, Sai S and Kerelsky, Alexander and Rubio-Verd{\'u}, Carmen and Shabani, Sara and Xian, Lede and Carr, Stephen and Chen, Shaowen and Zhang, Charles and others}
}
@article {hesp2021observation,
	title = {Observation of interband collective excitations in twisted bilayer graphene},
	journal = {Nature Physics},
	volume = {17},
	number = {10},
	year = {2021},
	pages = {1162{\textendash}1168},
	publisher = {Nature Publishing Group},
	doi = {10.1038/s41567-021-01327-8},
	author = {Hesp, Niels CH and Torre, Iacopo and Rodan-Legrain, Daniel and Novelli, Pietro and Cao, Yuan and Carr, Stephen and Fang, Shiang and Stepanov, Petr and Barcons-Ruiz, David and Herzig Sheinfux, Hanan and others}
}
@article {tang2021geometric,
	title = {Geometric origins of topological insulation in twisted layered semiconductors},
	journal = {Physical Review B},
	volume = {104},
	number = {15},
	year = {2021},
	pages = {155415},
	publisher = {APS},
	doi = {10.1103/PhysRevB.104.155415},
	author = {Tang, Hao and Carr, Stephen and Efthimios Kaxiras}
}
@article {zhang2021correlated,
	title = {Correlated insulating states and transport signature of superconductivity in twisted trilayer graphene superlattices},
	journal = {Physical Review Letters},
	volume = {127},
	number = {16},
	year = {2021},
	pages = {166802},
	publisher = {APS},
	doi = {10.1103/PhysRevLett.127.166802},
	author = {Zhang, Xi and Tsai, Kan-Ting and Zhu, Ziyan and Wei Ren and Luo, Yujie and Carr, Stephen and Luskin, Mitchell and Efthimios Kaxiras and Ke Wang}
}
@article {devarakonda2021signatures,
	title = {Signatures of bosonic Landau levels in a finite-momentum superconductor},
	journal = {Nature},
	volume = {599},
	number = {7883},
	year = {2021},
	pages = {51{\textendash}56},
	publisher = {Nature Publishing Group},
	doi = {10.1038/s41586-021-03915-3},
	author = {Devarakonda, A and T. Suzuki and Fang, S and Zhu, J and Graf, D and Kriener, M and Fu, L and E. Kaxiras and Checkelsky, JG}
}
@article {kuate2021theoretical,
	title = {Theoretical investigation of charge transfer between the NV- center in diamond and substitutional N and P},
	journal = {Journal of Applied Physics},
	volume = {130},
	number = {15},
	year = {2021},
	pages = {155102},
	publisher = {AIP Publishing LLC} doi=0.1063/5.0061396},
	author = {Defo, Rodrick Kuate and Zhang, Xingyu and Richardson, Steven L and Efthimios Kaxiras}
}
@article {pizzochero2021electrically,
	title = {Electrically Induced Dirac Fermions in Graphene Nanoribbons},
	journal = {Nano Letters},
	volume = {21},
	number = {21},
	year = {2021},
	pages = {9332{\textendash}9338},
	publisher = {ACS Publications},
	doi = {10.1021/acs.nanolett.1c03596},
	author = {Pizzochero, Michele and Tepliakov, Nikita V and Mostofi, Arash A and Efthimios Kaxiras}
}
@article {ledwith2021tb,
	title = {TB or not TB? Contrasting properties of twisted bilayer graphene and the alternating twist n-layer structures (n= 3, 4, 5, ...)},
	journal = {arXiv preprint: 2111.11060},
	year = {2021},
	doi = {10.48550/arXiv.2111.11060},
	author = {Ledwith, Patrick J and Khalaf, Eslam and Zhu, Ziyan and Carr, Stephen and Efthimios Kaxiras and Ashvin Vishwanath}
}
@article {chaves2021microscopic,
	title = {Microscopic origin of the high thermoelectric figure of merit of n-doped SnSe},
	journal = {Physical Review B},
	volume = {104},
	number = {11},
	year = {2021},
	pages = {115204},
	publisher = {APS},
	doi = {10.1103/PhysRevB.104.115204},
	author = {Chaves, Anderson S and Larson, Daniel T and Efthimios Kaxiras and Antonelli, Alex}
}
@article {zhang2021spectroscopic,
	title = {Spectroscopic Signatures of Interlayer Coupling in Janus MoSSe/MoS2 Heterostructures},
	journal = {ACS nano},
	volume = {15},
	number = {9},
	year = {2021},
	pages = {14394{\textendash}14403},
	publisher = {ACS Publications},
	doi = {10.1021/acsnano.1c03779},
	author = {Zhang, Kunyan and Guo, Yunfan and Larson, Daniel T and Zhu, Ziyan and Fang, Shiang and Efthimios Kaxiras and Jing Kong and Shengxi Huang}
}
@article {tritsaris2020electronic,
	title = {Electronic structure calculations of twisted multi-layer graphene superlattices},
	journal = {2D Materials},
	volume = {7},
	number = {3},
	year = {2020},
	pages = {035028},
	publisher = {IOP Publishing},
	doi = {10.1088/2053-1583/ab8f62},
	author = {Georgios A. Tritsaris and Carr, Stephen and Zhu, Ziyan and Xie, Yiqi and Torrisi, Steven B and Tang, Jing and Marios Mattheakis and Larson, Daniel T and Efthimios Kaxiras}
}
@article {tritsaris2020lan,
	title = {LAN: A materials notation for two-dimensional layered assemblies},
	journal = {Journal of Chemical Information and Modeling},
	volume = {60},
	number = {7},
	year = {2020},
	pages = {3457{\textendash}3462},
	publisher = {ACS Publications},
	doi = {10.1021/acs.jcim.0c00630},
	author = {Georgios A. Tritsaris and Xie, Yiqi and Rush, Alexander M and Carr, Stephen and Marios Mattheakis and Efthimios Kaxiras}
}
@article {zhang2020enhancement,
	title = {Enhancement of van der Waals interlayer coupling through polar Janus MoSSe},
	journal = {Journal of the American Chemical Society},
	volume = {142},
	number = {41},
	year = {2020},
	pages = {17499{\textendash}17507},
	publisher = {ACS Publications},
	doi = {10.1021/jacs.0c07051},
	author = {Zhang, Kunyan and Guo, Yunfan and Ji, Qingqing and Lu, Ang-Yu and Su, Cong and Wang, Hua and Puretzky, Alexander A and Geohegan, David B and Qian, Xiaofeng and Fang, Shiang and others}
}
@article {carr2020duality,
	title = {Duality between atomic configurations and Bloch states in twistronic materials},
	journal = {Physical Review Research},
	volume = {2},
	number = {3},
	year = {2020},
	pages = {033162},
	publisher = {APS},
	doi = {10.1103/PhysRevResearch.2.033162},
	author = {Carr, Stephen and Massatt, Daniel and Luskin, Mitchell and Efthimios Kaxiras}
}
@article {zhu2020modeling,
	title = {Modeling mechanical relaxation in incommensurate trilayer van der Waals heterostructures},
	journal = {Physical Review B},
	volume = {101},
	number = {22},
	year = {2020},
	pages = {224107},
	publisher = {APS},
	doi = {10.1103/PhysRevB.101.224107},
	author = {Zhu, Ziyan and Cazeaux, Paul and Luskin, Mitchell and Efthimios Kaxiras}
}
@article {carr2020electronic,
	title = {Electronic-structure methods for twisted moir{\'e} layers},
	journal = {Nature Reviews Materials},
	volume = {5},
	number = {10},
	year = {2020},
	pages = {748{\textendash}763},
	publisher = {Nature Publishing Group},
	doi = {10.1038/s41578-020-0214-0},
	author = {Carr, Stephen and Fang, Shiang and Efthimios Kaxiras}
}
@article {zhu2020twisted,
	title = {Twisted trilayer graphene: A precisely tunable platform for correlated electrons},
	journal = {Physical review letters},
	volume = {125},
	number = {11},
	year = {2020},
	pages = {116404},
	publisher = {APS},
	doi = {10.1103/PhysRevLett.125.116404},
	author = {Zhu, Ziyan and Carr, Stephen and Massatt, Daniel and Luskin, Mitchell and Efthimios Kaxiras}
}
@article {larson2020effects,
	title = {Effects of structural distortions on the electronic structure of T-type transition metal dichalcogenides},
	journal = {Physical Review B},
	volume = {102},
	number = {4},
	year = {2020},
	pages = {045128},
	publisher = {APS},
	doi = {10.1103/PhysRevB.102.045128},
	author = {Larson, Daniel T and Chen, Wei and Torrisi, Steven B and Jennifer Coulter and Fang, Shiang and Efthimios Kaxiras}
}
@article {rhone2020data,
	title = {Data-driven studies of magnetic two-dimensional materials},
	journal = {Scientific reports},
	volume = {10},
	number = {1},
	year = {2020},
	pages = {1{\textendash}11},
	publisher = {Nature Publishing Group},
	doi = {10.1038/s41598-020-72811-z},
	author = {Trevor David Rhone and Chen, Wei and Shaan Desai and Torrisi, Steven B and Larson, Daniel T and Amir Yacoby and Efthimios Kaxiras}
}
@article {larson2020effects,
	title = {Effects of lithium intercalation in twisted bilayer graphene},
	journal = {Physical Review B},
	volume = {101},
	number = {7},
	year = {2020},
	pages = {075407},
	publisher = {APS},
	doi = {10.1103/PhysRevB.101.075407},
	author = {Larson, Daniel T and Carr, Stephen and Georgios A. Tritsaris and Efthimios Kaxiras}
}
@article {lu2020lithium,
	title = {Lithium intercalation in MoS2 bilayers and implications for moir{\'e} flat bands},
	journal = {Physical Review B},
	volume = {102},
	number = {12},
	year = {2020},
	pages = {125424},
	publisher = {APS},
	doi = {10.1103/PhysRevB.102.125424},
	author = {Lu, Zheyu and Carr, Stephen and Larson, Daniel T and Efthimios Kaxiras}
}
@article {chaves2020boosting,
	title = {Boosting the efficiency of ab initio electron-phonon coupling calculations through dual interpolation},
	journal = {Physical Review B},
	volume = {102},
	number = {12},
	year = {2020},
	pages = {125116},
	publisher = {APS},
	doi = {10.1103/PhysRevB.102.125116},
	author = {Chaves, Anderson S and Antonelli, Alex and Larson, Daniel T and Efthimios Kaxiras}
}
@article {hoyt2019machine,
	title = {Machine learning prediction of H adsorption energies on Ag alloys},
	journal = {Journal of chemical information and modeling},
	volume = {59},
	number = {4},
	year = {2019},
	pages = {1357{\textendash}1365},
	publisher = {ACS Publications},
	doi = {10.1021/acs.jcim.8b00657},
	author = {Hoyt, Robert A and Montemore, Matthew M and Ioanna Fampiou and Chen, Wei and Georgios Tritsaris and Efthimios Kaxiras}
}
@article {fang2019angle,
	title = {Angle-Dependent Ab initio Low-Energy Hamiltonians for a Relaxed Twisted Bilayer Graphene Heterostructure},
	journal = {arXiv:1908.00058},
	year = {2019},
	doi = {10.48550/arXiv.1908.00058},
	author = {Fang, Shiang and Carr, Stephen and Zhu, Ziyan and Massatt, Daniel and Efthimios Kaxiras}
}
@article {carr2019exact,
	title = {Exact continuum model for low-energy electronic states of twisted bilayer graphene},
	journal = {Physical Review Research},
	volume = {1},
	number = {1},
	year = {2019},
	pages = {013001},
	publisher = {APS},
	doi = {10.1103/PhysRevResearch.1.013001},
	author = {Carr, Stephen and Fang, Shiang and Zhu, Ziyan and Efthimios Kaxiras}
}
@article {tritsaris2019first,
	title = {First-principles study of coupled effect of ripplocations and S-vacancies in MoS2},
	journal = {Journal of Applied Physics},
	volume = {126},
	number = {8},
	year = {2019},
	pages = {084303},
	publisher = {AIP Publishing LLC},
	doi = {10.1063/1.5099496},
	author = {Georgios A. Tritsaris and {\c S}ensoy, Mehmet G{\"o}khan and Shirodkar, Sharmila N and Efthimios Kaxiras}
}
@article {kuate2019carbon,
	title = {How carbon vacancies can affect the properties of group IV color centers in diamond: A study of thermodynamics and kinetics},
	journal = {Journal of Applied Physics},
	volume = {126},
	number = {19},
	year = {2019},
	pages = {195103},
	publisher = {AIP Publishing LLC},
	doi = {10.1063/1.5123227},
	author = {Defo, Rodrick Kuate and Efthimios Kaxiras and Richardson, Steven L}
}
@article {klein2019enhancement,
	title = {Enhancement of interlayer exchange in an ultrathin two-dimensional magnet},
	journal = {Nature Physics},
	volume = {15},
	number = {12},
	year = {2019},
	pages = {1255{\textendash}1260},
	publisher = {Nature Publishing Group},
	doi = {10.1038/s41567-019-0651-0},
	author = {Klein, Dahlia R and MacNeill, David and Song, Qian and Larson, Daniel T and Fang, Shiang and Xu, Mingyu and Ribeiro, Raquel A and Canfield, Paul C and Efthimios Kaxiras and Comin, Riccardo and others}
}
@article {644806,
	title = {Machine learning with observers predicts complex spatiotemporal behavior.},
	journal = {Front. Phys. - Quantum Computing},
	volume = {7},
	number = {24},
	year = {2019},
	pages = {1-9},
	abstract = {Chimeras and branching are two archetypical complex phenomena that appear in many physical systems; because of their different intrinsic dynamics, they delineate opposite non-trivial limits in the complexity of wave motion and present severe challenges in predicting chaotic and singular behavior in extended physical systems. We report on the long-term forecasting capability of Long Short-Term Memory (LSTM) and reservoir computing (RC) recurrent neural networks, when they are applied to the spatiotemporal evolution of turbulent chimeras in simulated arrays of coupled superconducting quantum interference devices (SQUIDs) or lasers, and branching in the electronic flow of two-dimensional graphene with random potential. We propose a new method in which we assign one LSTM network to each system node except for {\textquotedblleft}observer{\textquotedblright} nodes which provide continual {\textquotedblleft}ground truth{\textquotedblright} measurements as input; we refer to this method as {\textquotedblleft}Observer LSTM{\textquotedblright} (OLSTM). Wedemonstrate that even a small number of observers greatly improves the data-driven (model-free) long-term forecasting capability of the LSTM networks and provide the framework for a consistent comparison between the RC and LSTM methods. We find that RC requires smaller training datasets than OLSTMs, but the latter require fewer observers. Both methods are benchmarked against Feed-Forward neural networks (FNNs), also trained to make predictions with observers (OFNNs).},
	url = {https://www.frontiersin.org/articles/10.3389/fphy.2019.00024/full},
	author = {G. N. Neofotistos and M.Mattheakis and G. Barbaris and J. Hitzanidi and G. P. Tsironis and E. Kaxiras}
}
@article {644805,
	title = {Homogenization of plasmonic crystals: Seeking the epsilon-near-zero behavior.},
	journal = {Proceedings of the Royal Society A},
	volume = {475},
	number = {2230},
	year = {2019},
	abstract = {By using an asymptotic analysis and numerical simulations, we derive and investigate a system of homogenized Maxwell{\textquoteright}s equations for conducting material sheets that are periodically arranged and embedded in a heterogeneous and anisotropic dielectric host.\&amp;nbsp; This structure is motivated by the need to design plasmonic crystals that enable the propagation of electromagnetic waves with no phase delay (epsilon-near-zero effect). Our microscopic model incorporates the surface conductivity of the two-dimensional (2D) material of each sheet and a corresponding line charge density through a line conductivity along possible edges of the sheets. Our analysis generalizes averaging principles inherent in previous Bloch-wave approaches. We investigate physical implications of our findings. In particular, we emphasize the role of the vector-valued corrector field, which expresses microscopic modes of surface waves on the 2D material. By using a Drude model for the surface conductivity of the sheet, we construct a Lorentzian function that describes the effective dielectric permittivity tensor of the plasmonic crystal as a function of frequency.},
	url = {https://royalsocietypublishing.org/doi/10.1098/rspa.2019.0220},
	author = {M. Maier and M.Mattheakis and E. Kaxiras and M. Luskin and D. Margetis}
}
@article { ISI:000449171600001,
	title = {High performance tunnel field effect transistors based on in-plane transition metal dichalcogenide heterojunctions},
	journal = {NANOTECHNOLOGY},
	volume = {30},
	number = {2},
	year = {2019},
	month = {JAN 11},
	abstract = {In-plane heterojunction tunnel field effect transistors based on monolayer transition metal dichalcogenides are studied by means of self-consistent non-equilibrium Green{\textquoteright}s functions simulations and an atomistic tight-binding Hamiltonian. We start by comparing several heterojunctions before focusing on the most promising ones, i.e. WTe2-MoS2 and MoTe2-MoS2. The scalability of those devices as a function of channel length is studied, and the influence of backgate voltages on device performance is analyzed. Our results indicate that, by fine-tuning the design parameters, those devices can yield extremely low subthreshold swings (,
	issn = {0957-4484},
	doi = {10.1088/1361-6528/aae7df},
	author = {Choukroun, Jean and Pala, Marco and Fang, Shiang and Efthimios Kaxiras and Dollfus, Philippe}
}
@article { ISI:000455781600037,
	title = {Observation of the nonlinear Hall effect under time-reversal-symmetric conditions},
	journal = {NATURE},
	volume = {565},
	number = {7739},
	year = {2019},
	month = {JAN 17},
	pages = {337+},
	abstract = {The electrical Hall effect is the production, upon the application of an electric field, of a transverse voltage under an out-of-plane magnetic field. Studies of the Hall effect have led to important breakthroughs, including the discoveries of Berry curvature and topological Chern invariants(1,2). The internal magnetization of magnets means that the electrical Hall effect can occur in the absence of an external magnetic field(2); this {\textquoteleft}anomalous{\textquoteright} Hall effect is important for the study of quantum magnets(2-7). The electrical Hall effect has rarely been studied in non-magnetic materials without external magnetic fields, owing to the constraint of timer-eversal symmetry. However, only in the linear response regime-when the Hall voltage is linearly proportional to the external electric field-does the Hall effect identically vanish as a result of time-reversal symmetry; the Hall effect in the nonlinear response regime is not subject to such symmetry constraints(8-10). Here we report observations of the nonlinear Hall effect(10) in electrical transport in bilayers of the non-magnetic quantum material WTe2 under time-reversal-symmetric conditions. We show that an electric current in bilayer WTe2 leads to a nonlinear Hall voltage in the absence of a magnetic field. The properties of this nonlinear Hall effect are distinct from those of the anomalous Hall effect in metals: the nonlinear Hall effect results in a quadratic, rather than linear, current-voltage characteristic and, in contrast to the anomalous Hall effect, the nonlinear Hall effect results in a much larger transverse than longitudinal voltage response, leading to a nonlinear Hall angle (the angle between the total voltage response and the applied electric field) of nearly 90 degrees. We further show that the nonlinear Hall effect provides a direct measure of the dipole moment(10) of the Berry curvature, which arises from layer-polarized Dirac fermions in bilayer WTe2. Our results demonstrate a new type of Hall effect and provide a way of detecting Berry curvature in nonmagnetic quantum materials.},
	issn = {0028-0836},
	doi = {10.1038/s41586-018-0807-6},
	author = {Qiong Ma and Xu, Su-Yang and Shen, Huitao and MacNeill, David and Fatemi, Valla and Chang, Tay-rong and Valdivia, Andres M. Mier and Wu, Sanfeng and Du, Zongzheng and Hsu, Chuang-Han and Fang, Shiang and Gibson, Quinn D. and Kenji Watanabe and Takashi Taniguchi and Cava, Robert J. and Efthimios Kaxiras and Lu, Hai-Zhou and Lin, Hsin and Liang Fu and Gedik, Nuh and Pablo Jarillo-Herrero}
}
@article { ISI:000446141900028,
	title = {Anhydrous Methanol and Ethanol Dehydrogenation at Cu(111) Step Edges},
	journal = {JOURNAL OF PHYSICAL CHEMISTRY C},
	volume = {122},
	number = {38},
	year = {2018},
	month = {SEP 27},
	pages = {21952-21962},
	abstract = {Oxidative methanol dehydrogenation is a major industrial reaction with global formaldehyde production exceeding 30 million tonnes per year. Unfortunately, oxidative dehydrogenation produces water aldehyde mixtures that require subsequent distillation. Anhydrous alcohol dehydrogenation is a promising alternative that produces H-2 instead of water. Pursuant to recent experimental work showing that highly stepped Cu(111) surfaces exhibit anhydrous dehydrogenation activity, we present first-principles density functional theory calculations for methanol and ethanol dehydrogenation at Cu(111) step edges to provide an atomistic understanding of the catalytic mechanism; these sites stabilize all intermediates while reducing activation energies. We find that van der Waals contributions to the energy account for more than 50\% of adsorption energies, and essential in achieving good agreement with experimental desorption temperatures. Furthermore, vibrational zero-point energy corrections significantly reduce the activation energy for all reaction steps considered here. Hydrogen bonding among ethanol intermediates at step edges is weakened by geometric frustration. These insights lead us to propose several suggestions for further research on undercoordinated Cu sites as anhydrous alcohol dehydrogenation catalysts.},
	issn = {1932-7447},
	doi = {10.1021/acs.jpcc.8b06730},
	author = {Hoyt, Robert A. and Montemore, Matthew M. and Sykes, E. Charles H. and Efthimios Kaxiras}
}
@article { ISI:000445597200001,
	title = {Berry curvature dipole current in the transition metal dichalcogenides family},
	journal = {PHYSICAL REVIEW B},
	volume = {98},
	number = {12},
	year = {2018},
	month = {SEP 25},
	abstract = {We study the quantum nonlinear Hall effect in two-dimensional (2D) materials with time-reversal symmetry. When only one mirror line exists, a transverse charge current occurs in the second-order response to an external electric field, as a result of the Berry curvature dipole in momentum space. Candidate 2D materials to observe this effect are two-dimensional transition metal dichalcogenides (TMDCs). First, we use an ab initio based tight-binding approach to demonstrate that monolayer T-d-structure TMDCs exhibit a finite Berry curvature dipole. In the 1H and 1T{\textquoteright} phase of TMDCs, we show the emergence of a finite Berry curvature dipole with the application of strain and an electrical displacement field, respectively.},
	issn = {2469-9950},
	doi = {10.1103/PhysRevB.98.121109},
	author = {You, Jhih-Shih and Fang, Shiang and Xu, Su-Yang and Efthimios Kaxiras and Low, Tony}
}
@article { ISI:000430255900029,
	title = {A Comparative Ab Initio Study of Anhydrous Dehydrogenation of Linear-Chain Alcohols on Cu(110)},
	journal = {JOURNAL OF PHYSICAL CHEMISTRY C},
	volume = {122},
	number = {14},
	year = {2018},
	month = {APR 12},
	pages = {7806-7815},
	abstract = {The catalytic behavior of Cu surfaces in the anhydrous production of aldehydes from alcohols, a process of industrial significance, is puzzling: the two simplest alcohols (methanol and ethanol) show dramatically different decomposition behavior on Cu. Here, we study the thermodynamic and kinetic processes involved in the anhydrous dehydrogenation of linear-chain alcohols including methanol, ethanol, 1-propanol, and 1-butanol on the Cu(110) surface using multiscale approaches. First, we obtain the adsorption structures and energies of the reaction intermediates, in which van der Waals (vdW) interactions play a crucial role. Then, we determine the kinetic barriers for the two dehydrogenation steps, namely, the O-H and the subsequent C-H bond-breaking on Cu. The reaction of methoxy-to-formaldehyde has a rather high-energy transition state, in contrast to that of alkoxide-to-aldehyde in the longer-chain systems. This difference qualitatively explains the lower production efficiency of formaldehyde on Cu. Finally, we simulate the production rates of aldehydes based on which we optimize reaction conditions and propose possible avenues for enhancing the production of anhydrous formaldehyde using Cu-based catalysts.},
	issn = {1932-7447},
	doi = {10.1021/acs.jpcc.8b01698},
	author = {Chen, Wei and Ekin Dogus Cubuk and Montemore, Matthew M. and Reece, Christian and Madix, Robert J. and Cynthia M. Friend and Efthimios Kaxiras}
}
@article { ISI:000437380000004,
	title = {Compression of Wannier functions into Gaussian-type orbitals},
	journal = {COMPUTER PHYSICS COMMUNICATIONS},
	volume = {230},
	year = {2018},
	month = {SEP},
	pages = {27-37},
	abstract = {We propose a greedy algorithm for the compression of Wannier functions into Gaussian-polynomials orbitals. The so-obtained compressed Wannier functions can be stored in a very compact form, and can be used to efficiently parameterize effective tight-binding Hamiltonians for multilayer 2D materials for instance. The compression method preserves the symmetries (if any) of the original Wannier function. We provide algorithmic details, and illustrate the performance of our implementation on several examples, including graphene, hexagonal boron-nitride, single-layer FeSe, and bulk silicon in the diamond cubic structure. (C) 2018 Elsevier B.V. All rights reserved.},
	issn = {0010-4655},
	doi = {10.1016/j.cpc.2018.04.011},
	author = {Bakhta, Athmane and Cances, Eric and Cazeaux, Paul and Fang, Shiang and Efthimios Kaxiras}
}
@article { ISI:000429103300038,
	title = {Correlated insulator behaviour at half-filling in magic-angle graphene superlattices},
	journal = {NATURE},
	volume = {556},
	number = {7699},
	year = {2018},
	month = {APR 5},
	pages = {80+},
	abstract = {A van der Waals heterostructure is a type of metamaterial that consists of vertically stacked two-dimensional building blocks held together by the van der Waals forces between the layers. This design means that the properties of van der Waals heterostructures can be engineered precisely, even more so than those of two-dimensional materials(1). One such property is the {\textquoteleft}twist{\textquoteright} angle between different layers in the heterostructure. This angle has a crucial role in the electronic properties of van der Waals heterostructures, but does not have a direct analogue in other types of heterostructure, such as semiconductors grown using molecular beam epitaxy. For small twist angles, the moire pattern that is produced by the lattice misorientation between the two-dimensional layers creates long-range modulation of the stacking order. So far, studies of the effects of the twist angle in van der Waals heterostructures have concentrated mostly on heterostructures consisting of monolayer graphene on top of hexagonal boron nitride, which exhibit relatively weak interlayer interaction owing to the large bandgap in hexagonal boron nitride(2-5). Here we study a heterostructure consisting of bilayer graphene, in which the two graphene layers are twisted relative to each other by a certain angle. We show experimentally that, as predicted theoretically(6), when this angle is close to the {\textquoteleft}magic{\textquoteright} angle the electronic band structure near zero Fermi energy becomes flat, owing to strong interlayer coupling. These flat bands exhibit insulating states at half-filling, which are not expected in the absence of correlations between electrons. We show that these correlated states at half-filling are consistent with Mott-like insulator states, which can arise from electrons being localized in the superlattice that is induced by the moire pattern. These properties of magic-angle-twisted bilayer graphene heterostructures suggest that these materials could be used to study other exotic many-body quantum phases in two dimensions in the absence of a magnetic field. The accessibility of the flat bands through electrical tunability and the bandwidth tunability through the twist angle could pave the way towards more exotic correlated systems, such as unconventional superconductors and quantum spin liquids.},
	issn = {0028-0836},
	doi = {10.1038/nature26154},
	author = {Cao, Yuan and Fatemi, Valla and Demir, Ahmet and Fang, Shiang and Tomarken, Spencer L. and Luo, Jason Y. and Sanchez-Yamagishi, Javier D. and Kenji Watanabe and Takashi Taniguchi and Efthimios Kaxiras and Ashoori, Ray C. and Pablo Jarillo-Herrero}
}
@article { ISI:000449909600001,
	title = {Density functional theory beyond the Born-Oppenheimer approximation: Accurate treatment of the ionic zero-point motion},
	journal = {PHYSICAL REVIEW B},
	volume = {98},
	number = {19},
	year = {2018},
	month = {NOV 12},
	abstract = {We introduce a method to carry out zero-temperature calculations within density functional theory (DFT) but without relying on the Born-Oppenheimer (BO) approximation for the ionic motion. Our approach is based on the finite-temperature many-body path-integral formulation of quantum mechanics by taking the zero-temperature limit and treating the imaginary-time propagation of the electronic variables in the context of DFT. This goes beyond the familiar BO approximation and is limited from being an exact treatment of both electrons and ions only by the approximations involved in the DFT component. We test our method in two simple molecules, H-2 and benzene. We demonstrate that the method produces a difference from the results of the BO approximation which is significant for many physical systems, especially those containing light atoms such as hydrogen; in these cases, we find that the fluctuations of the distance from its equilibrium position, due to the zero-point motion, is comparable to the interatomic distances. The method is suitable for use with conventional condensed-matter approaches and currently is implemented on top of the periodic pseudopotential code SIESTA.},
	issn = {2469-9950},
	doi = {10.1103/PhysRevB.98.195112},
	author = {Grigory Kolesov and Efthimios Kaxiras and Manousakis, Efstratios}
}
@article { ISI:000452007300003,
	title = {Dihedral-angle-corrected registry-dependent interlayer potential for multilayer graphene structures},
	journal = {PHYSICAL REVIEW B},
	volume = {98},
	number = {23},
	year = {2018},
	month = {DEC 4},
	abstract = {The structural relaxation of multilayer graphene is essential in describing the interesting electronic properties induced by intentional misalignment of successive layers, including the recently reported superconductivity in twisted bilayer graphene. This is difficult to accomplish without an accurate interatomic potential. Here, we present a new, registry-dependent Kolmogorov-Crespi-type interatomic potential to model interlayer interactions in multilayer graphene structures. It consists of two parts, representing attractive interaction due to dispersion and repulsive interaction due to anisotropic overlap of electronic orbitals. An important new feature is a dihedral-angle-dependent term that is added to the repulsive part to describe correctly several distinct stacking states that the original Kolmogorov-Crespi potential cannot distinguish. We refer to the new model as the dihedral-angle-corrected registry-dependent interlayer potential (DRIP). Computations for several test problems show that DRIP correctly reproduces the binding, sliding, and twisting energies and forces obtained from ab initio total-energy calculations based on density-functional theory. We use the new potential to study the structural properties of a twisted graphene bilayer and the exfoliation of graphene from graphite. Our potential is available through the OpenKIM interatomic potential repository at https://openkim org.},
	issn = {2469-9950},
	doi = {10.1103/PhysRevB.98.235404},
	author = {Wen, Mingjian and Carr, Stephen and Fang, Shiang and Efthimios Kaxiras and Tadmor, Ellad B.}
}
@article { ISI:000430866200005,
	title = {Dry Dehydrogenation of Ethanol on Pt-Cu Single Atom Alloys},
	journal = {TOPICS IN CATALYSIS},
	volume = {61},
	number = {5-6, SI},
	year = {2018},
	month = {MAY},
	pages = {328-335},
	abstract = {The non-oxidative dehydrogenation of ethanol to acetaldehyde and hydrogen is an industrially relevant chemical conversion. Although Cu-based catalysts show high reactivity toward oxidative ethanol dehydrogenation, the flat Cu(111) surface is rather inactive for ethanol dehydrogenation in the absence of water, surface oxygen or defects. Herein we show, using experimental and theoretical studies of model systems, that adding 1\% Pt into the surface of Cu(111) to form dilute Pt-Cu single atom alloys (SAAs) increases the activity of Cu(111) for ethanol dehydrogenation sixfold. The mechanism of ethanol dehydrogenation was investigated at the molecular level using scanning tunneling microscopy, temperature programmed experiments and density functional theory calculations. Our results demonstrate that Pt-Cu SAAs are much more active than Cu(111) for converting ethanol to acetaldehyde and hydrogen in the absence of surface oxygen and water. Specifically, the O-H bond of ethanol is activated at Pt sites below 160 K, followed by ethoxy spillover to Cu sites which results in a significant increase of the ethoxy intermediate yield. The C-H bond of ethoxy is then activated at 310 K, and the final product, acetaldehyde, desorbs from Cu(111) in a reaction rate limited process. Finally, we show that the Cu model surfaces exhibit stability with respect to poisoning as well as 100\% selectivity in the alcohol dehydrogenation to acetaldehyde and hydrogen.},
	issn = {1022-5528},
	doi = {10.1007/s11244-017-0856-3},
	author = {Wang, Zhi-Tao and Hoyt, Robert A. and El-Soda, Mostafa and Madix, Robert J. and Efthimios Kaxiras and Sykes, E. Charles H.}
}
@article { ISI:000440820800001,
	title = {Electronic structure theory of strained two-dimensional materials with hexagonal symmetry},
	journal = {PHYSICAL REVIEW B},
	volume = {98},
	number = {7},
	year = {2018},
	month = {AUG 6},
	abstract = {We derive electronic tight-binding Hamiltonians for strained graphene, hexagonal boron nitride, and transition-metal dichalcogenides based on Wannier transformation of ab initio density functional theory calculations. Our microscopic models include strain effects to leading order that respect the hexagonal crystal symmetry and local crystal configuration and are beyond the central force approximation which assumes only pairwise distance dependence. Based on these models, we also derive and analyze the effective low-energy Hamiltonians. Our ab initio approaches complement the symmetry group representation construction for such effective low-energy Hamiltonians and provide the values of the coefficients for each symmetry-allowed term. These models are relevant for the design of electronic device applications since they provide the framework for describing the coupling of electrons to other degrees of freedom including phonons, spin, and the electromagnetic field. The models can also serve as the basis for exploring the physics of many-body systems of interesting quantum phases.},
	issn = {2469-9950},
	doi = {10.1103/PhysRevB.98.075106},
	author = {Fang, Shiang and Carr, Stephen and Cazalilla, Miguel A. and Efthimios Kaxiras}
}
@article { ISI:000435680100001,
	title = {Emergence and dynamical properties of stochastic branching in the electronic flows of disordered Dirac solids},
	journal = {EPL},
	volume = {122},
	number = {2},
	year = {2018},
	month = {APR},
	abstract = {Graphene as well as more generally Dirac solids constitute two-dimensional materials where the electronic flow is ultra-relativistic. When a Dirac solid is deposited on a different substrate surface with roughness, a local random potential develops through an inhomogeneous charge impurity distribution. This external potential affects profoundly the charge flow and induces a chaotic pattern of current branches that develops through focusing and defocusing effects produced by the randomness of the surface. An additional bias voltage may be used to tune the branching pattern of the charge carrier currents. We employ analytical and numerical techniques in order to investigate the onset and the statistical properties of carrier branches in Dirac solids. We find a specific scaling-type relationship that connects the physical scale for the occurrence of branches with the characteristic medium properties, such as disorder and bias field. We use numerics to test and verify the theoretical prediction as well as a perturbative approach that gives a clear indication of the regime of validity of the approach. This work is relevant to device applications and may be tested experimentally.},
	issn = {0295-5075},
	doi = {10.1209/0295-5075/122/27003},
	author = {Marios Mattheakis and G. P. Tsironis and Efthimios Kaxiras}
}
@article { ISI:000443671700003,
	title = {Energetics and kinetics of vacancy defects in 4H-SiC},
	journal = {PHYSICAL REVIEW B},
	volume = {98},
	number = {10},
	year = {2018},
	month = {SEP 4},
	abstract = {Defect engineering in wide-gap semiconductors is important in controlling the performance of single-photon emitter devices. The effective incorporation of defects depends strongly on the ability to control their formation and location, as well as to mitigate attendant damage to the material. In this study, we combine density functional theory, molecular dyamics (MD), and kinetic Monte Carlo (KMC) simulations to study the energetics and kinetics of the silicon monovacancy V-Si and related defects in 4H-SiC. We obtain the defect formation energy for V-Si in various charge states and use MD simulations to model the ion implantation process for creating defects. We also study the effects of high-temperature annealing on defect position and stability using KMC and analytical models. Using a larger (480-atom) supercell than previous studies, we obtain the temperature-dependent diffusivity of V-Si in various charge states and find significantly lower barriers to diffusion than previous estimates. In addition, we examine the recombination with interstitial Si and conversion of V-Si into CSiVC during annealing and propose methods for using strain to reduce changes in defect concentrations. Our results provide guidance for experimental efforts to control the position and density of V-Si defects within devices, helping to realize their potential as solid-state qubits.},
	issn = {2469-9950},
	doi = {10.1103/PhysRevB.98.104103},
	author = {Defo, Rodrick Kuate and Zhang, Xingyu and Bracher, David and Gunn Kim and Hu, Evelyn and Efthimios Kaxiras}
}
@article { ISI:000439299200003,
	title = {Enhanced superconductivity upon weakening of charge density wave transport in 2H-TaS2 in the two-dimensional limit},
	journal = {PHYSICAL REVIEW B},
	volume = {98},
	number = {3},
	year = {2018},
	month = {JUL 20},
	abstract = {Layered transition-metal dichalcogenides that host coexisting charge-density wave (CDW) and superconducting orders provide ideal systems for exploring the effects of dimensionality on correlated electronic phases. Dimensionality has a profound effect on both superconductivity and CDW instabilities. Here we report a substantial enhancement of the superconducting T-c to 3.4 K for 2H-TaS2 in the monolayer limit, compared to 0.8 K in the bulk. In addition, the transport signature of a CDW phase transition vanishes in the two-dimensional limit. In our analysis of electronic and vibrational properties of this material, we show that a reduction of the CDW amplitude results in a substantial increase of the density of states at the Fermi energy, which can boost T, by an amount similar to that seen in experiment. Our results indicate competition between CDW order and superconductivity in ultrathin 2H-TaS2 down to the monolayer limit, providing insight toward understanding correlated electronic phases in reduced dimensions.},
	issn = {2469-9950},
	doi = {10.1103/PhysRevB.98.035203},
	author = {Yang, Yafang and Fang, Shiang and Fatemi, Valla and Ruhman, Jonathan and Navarro-Moratalla, Efren and Kenji Watanabe and Takashi Taniguchi and Efthimios Kaxiras and Pablo Jarillo-Herrero}
}
@article { ISI:000423140600019,
	title = {General Effect of van der Waals Interactions on the Stability of Alkoxy Intermediates on Metal Surfaces},
	journal = {JOURNAL OF PHYSICAL CHEMISTRY B},
	volume = {122},
	number = {2, SI},
	year = {2018},
	month = {JAN 18},
	pages = {555-560},
	abstract = {The critical role of noncovalent van der Waals (vdW) interactions in determining the relative thermodynamic stability of alkoxy intermediates has been demonstrated for the Cu(110) surface using a combination of experiment and theory. The results may be significant for the selectivity control of copper-based reactions of alcohols. Previous examination of this effect on Au(110) was also extended to include higher molecular weight alcohols; on Cu(110) and Au(110) the hierarchy for the strength of binding of the alkoxys was found to be the same within experimental accuracy, with alkoxy species of greater chain length being more stable. The equilibrium constants governing the competition of alcohol pairs for binding sites of the alkoxys are also similar on the two surfaces. These results reveal the generality of such vdW effects. This work expands the understanding of the role of vdW interactions on the binding efficacy of key reactive intermediates on metal surfaces, a key factor in the rational design of complex and selective catalytic processes.},
	issn = {1520-6106},
	doi = {10.1021/acs.jpcb.7b04952},
	author = {Yunfei Xu and Chen, Wei and Efthimios Kaxiras and Cynthia M. Friend and Madix, Robert J.}
}
@article { ISI:000436037800046,
	title = {Heterointerface effects in the electrointercalation of van der Waals heterostructures},
	journal = {NATURE},
	volume = {558},
	number = {7710},
	year = {2018},
	month = {JUN 21},
	pages = {425+},
	abstract = {Molecular-scale manipulation of electronic and ionic charge accumulation in materials is the backbone of electrochemical energy storagel(1-4). Layered van der Waals (vdW) crystals are a diverse family of materials into which mobile ions can electrochemically intercalate into the interlamellar gaps of the host atomic lattice(5,6). The structural diversity of such materials enables the interfacial properties of composites to be optimized to improve ion intercalation for energy storage and electronic devices(7-12). However, the ability of heterolayers to modify intercalation reactions, and their role at the atomic level, are yet to be elucidated. Here we demonstrate the electrointercalation of lithium at the level of individual atomic interfaces of dissimilar vdW layers. Electrochemical devices based on vdW heterostructures(13) of stacked hexagonal boron nitride, graphene and molybdenum dichalcogenide (MoX2;X=S, Se) layers are constructed. We use transmission electron microscopy, in situ magnetoresistance and optical spectroscopy techniques, as well as low-temperature quantum magneto-oscillation measurements and ab initio calculations, to resolve the intermediate stages of lithium intercalation at heterointerfaces. The formation of vdW heterointerfaces between graphene and MoX2 results in a more than tenfold greater accumulation of charge in MoX2 when compared to MoX2/MoX2 homointerfaces, while enforcing a more negative intercalation potential than that of bulk MoX2 by at least 0.5 V. Beyond energy storage, our combined experimental and computational methodology for manipulating and characterizing the electrochemical behaviour of layered systems opens new pathways to control the charge density in two-dimensional electronic and optoelectronic devices.},
	issn = {0028-0836},
	doi = {10.1038/s41586-018-0205-0},
	author = {Bediako, D. Kwabena and Rezaee, Mehdi and Yoo, Hyobin and Larson, Daniel T. and Zhao, S. Y. Frank and Takashi Taniguchi and Kenji Watanabe and Brower-Thomas, Tina L. and Efthimios Kaxiras and Philip Kim}
}
@article { ISI:000431389300017,
	title = {Identifying key descriptors in surface binding: interplay of surface anchoring and intermolecular interactions for carboxylates on Au(110)},
	journal = {CHEMICAL SCIENCE},
	volume = {9},
	number = {15},
	year = {2018},
	month = {APR 21},
	pages = {3759-3766},
	abstract = {The relative stability of carboxylates on Au(110) was investigated as part of a comprehensive study of adsorbate binding on Group IB metals that can be used to predict and understand how to control reactivity in heterogeneous catalysis. The binding efficacy of carboxylates is only weakly dependent on alkyl chain length for relatively short-chain molecules, as demonstrated using quantitative temperature-programmed reaction spectroscopy. Corresponding density functional theory (DFT) calculations demonstrated that the bidentate anchoring geometry is rigid and restricts the amount of additional stabilization through adsorbate-surface van der Waals (vdW) interactions which control stability for alkoxides. A combination of scanning tunneling microscopy (STM) and low-energy electron diffraction (LEED) shows that carboxylates form dense local islands on Au(110). Complementary DFT calculations demonstrate that adsorbate-adsorbate interactions provide additional stabilization that increases as a function of alkyl chain length for C-2 and C-3 carboxylates. Hence, overall stability is generally a function of the anchoring group to the surface and the inter-adsorbate interaction. This study demonstrates the importance of these two important factors in describing binding of key catalytic intermediates.},
	issn = {2041-6520},
	doi = {10.1039/c7sc05313d},
	author = {O{\textquoteright}Connor, Christopher R. and Fanny Hiebel and Chen, Wei and Efthimios Kaxiras and Madix, Robert J. and Cynthia M. Friend}
}
@article { ISI:000427815800001,
	title = {Implanted neural network potentials: Application to Li-Si alloys},
	journal = {PHYSICAL REVIEW B},
	volume = {97},
	number = {9},
	year = {2018},
	month = {MAR 20},
	abstract = {Modeling the behavior of materials composed of elements with different bonding and electronic structure character for large spatial and temporal scales and over a large compositional range is a challenging problem. Cases in point are amorphous alloys of Si, a prototypical covalent material, and Li, a prototypical metal, which are being considered as anodes for high-energy-density batteries. To address this challenge, we develop a methodology based on neural networks that extends the conventional training approach to incorporate pre-trained parts that capture the character of different components, into the overall network; we refer to this model as the {\textquoteleft}{\textquoteleft}implanted neural network{\textquoteright}{\textquoteright} method. We show that this approach works well for the Si-Li amorphous alloys for a wide range of compositions, giving good results for key quantities like the diffusion coefficients. The method is readily generalizable to more complicated situations that involve two or more different elements.},
	issn = {2469-9950},
	doi = {10.1103/PhysRevB.97.094106},
	author = {Onat, Berk and Ekin D. Cubuk and Malone, Brad D. and Efthimios Kaxiras}
}
@article { ISI:000449308400005,
	title = {Lithium Intercalation in Graphene-MoS2 Heterostructures},
	journal = {JOURNAL OF PHYSICAL CHEMISTRY C},
	volume = {122},
	number = {43},
	year = {2018},
	month = {NOV 1},
	pages = {24535-24541},
	abstract = {Two-dimensional (2D) heterostructures are interesting candidates for efficient energy storage devices due to their high carrier capacity by reversible intercalation. We employ here density functional theory calculations to investigate the structural and electronic properties of lithium intercalated graphene/molybdenum disulfide (Gr/MoS2) heterostructures. We explore the extent to which Li intercalates at the interface formed between graphene (Gr) and molybdenum disulfide (MoS2) layers by considering the adsorption and diffusion of Li atoms, the energetic stability, and the changes in the structural morphology of MoS2. We investigate the corresponding electronic structure and charge distribution within the heterostructure at varying concentrations of Li. Our results indicate that the maximum energetically allowed ratio of Li to Mo (Li to C) is 1:1 (1:3) for both the 2H and 1T{\textquoteright} phases of MoS2. This is double the Li concentration allowed in graphene bilayers. We find that there is 60\% more charge transfer to MoS2 than to Gr in the bilayer heterostructure, which results in a maximum doping of Gr and MoS2 of n(C) = 3.6 x 10(14) cm(-2) and n(MoS2) = 6.0 x 10(14) cm(-2), respectively.},
	issn = {1932-7447},
	doi = {10.1021/acs.jpcc.8b07548},
	author = {Larson, Daniel T. and Ioanna Fampiou and Gunn Kim and Efthimios Kaxiras}
}
@conference { ISI:000451429100013,
	title = {Modeling Electronic Properties of Twisted 2D Atomic Heterostructures},
	booktitle = {COUPLED MATHEMATICAL MODELS FOR PHYSICAL AND BIOLOGICAL NANOSCALE SYSTEMS AND THEIR APPLICATIONS},
	series = {Springer Proceedings in Mathematics \& Statistics},
	volume = {232},
	year = {2018},
	note = {Banff International Research Station (BIRS) Workshop on Coupled Mathematical Models for Physical and Biological Nanoscale Systems and Their Applications, Banff, CANADA, AUG 28-SEP 02, 2016},
	pages = {245-265},
	publisher = {Banff Int Res Stat},
	organization = {Banff Int Res Stat},
	abstract = {We present a general method for the electronic characterization of aperiodic 2D materials using ab-initio tight binding models. Specifically studied is the subclass of twisted, stacked heterostructures, but the formalism provided can be implemented for any 2D system without long-range interactions. This new method provides a multi-scale approach for dealing with the ab-initio calculation of electronic transport properties in stacked nanomaterials, allowing for fast and efficient simulation of multi-layered stacks in the presence of twist angles, magnetic field, and defects. We calculate the electronic density of states in twisted bilayer systems of graphene and MX2 transition metal dichalcogenides (TMDCs). We comment on the interesting features of their density of states as a function of twist-angle and local configuration and how these features are experimentally observable. These results support the bilayer twist-angle as a new variable for controlling electronic properties in artificial nanomaterials ({\textquoteright}{\textquoteright}Twistronics{\textquoteright}{\textquoteright}).},
	isbn = {978-3-319-76599-0; 978-3-319-76598-3},
	issn = {2194-1009},
	doi = {10.1007/978-3-319-76599-0\_13},
	author = {Carr, Stephen and Massatt, Daniel and Fang, Shiang and Cazeaux, Paul and Luskin, Mitchell and Efthimios Kaxiras},
	editor = {Bonilla, LL and E. Kaxiras and Melnik, R}
}
@article { ISI:000444793500098,
	title = {New Pathway for Hot Electron Relaxation in Two-Dimensional Heterostructures},
	journal = {NANO LETTERS},
	volume = {18},
	number = {9},
	year = {2018},
	month = {SEP},
	pages = {6057-6063},
	abstract = {Two-dimensional (2D) heterostructures composed of transition-metal dichalcogenide atomic layers are the new frontier for novel optoelectronic and photovoltaic device applications. Some key properties that make these materials appealing, yet are not well understood, are ultrafast hole/electron dynamics, interlayer energy transfer and the formation of interlayer hot excitons. Here, we study photoexcited electron/hole dynamics in a representative heterostructure, the MoS2/WSe2 interface, which exhibits type II band alignment. Employing time-dependent density functional theory in the time domain, we observe ultrafast charge dynamics with lifetimes of tens to hundreds of femtoseconds. Most importantly, we report the discovery of an interfacial pathway in 2D heterostructures for the relaxation of photoexcited hot electrons through interlayer hopping, which is significantly faster than intralayer relaxation. This finding is of particular importance for understanding many experimentally observed photoinduced processes, including charge and energy transfer at an ultrafast time scale (,
	issn = {1530-6984},
	doi = {10.1021/acs.nanolett.8b03005},
	author = {Zhang, Jin and Hong, Hao and Zhang, Jia and Fu, Huixia and You, Peiwei and Lischner, Johannes and Liu, Kaihui and Efthimios Kaxiras and Sheng Meng}
}
@article { ISI:000445713200021,
	title = {Nonadiabatic Hydrogen Dissociation on Copper Nanoclusters},
	journal = {JOURNAL OF PHYSICAL CHEMISTRY LETTERS},
	volume = {9},
	number = {18},
	year = {2018},
	month = {SEP 20},
	pages = {5339+},
	abstract = {Copper surfaces exhibit high catalytic selectivity but have poor hydrogen dissociation kinetics; therefore, we consider icosahedral Cu-13 nanoclusters to understand how nanoscale structure might improve catalytic prospects. We find that the spin state is a surprisingly important design consideration. Cu-13 clusters have large magnetic moments due to finite size and symmetry effects and exhibit magnetization-dependent catalytic behavior. The most favorable transition state for hydrogen dissociation has a lower activation energy than that on single-crystal copper surfaces but requires a magnetization switch from 5 to 3 mu(B). Without this switch, the activation energy is higher than that on single-crystal surfaces. Weak spin-orbit coupling hinders this switch, decreasing the kinetic rate of hydrogen dissociation by a factor of 16. We consider strategies to facilitate magnetization switches through optical excitations, substitution, charge states, and co-catalysts; these considerations demonstrate how control of magnetic properties could improve catalytic performance.},
	issn = {1948-7185},
	doi = {10.1021/acs.jpclett.8b02133},
	author = {Hoyt, Robert A. and Montemore, Matthew M. and Efthimios Kaxiras}
}
@article { ISI:000442875900001,
	title = {Pressure dependence of the magic twist angle in graphene superlattices},
	journal = {PHYSICAL REVIEW B},
	volume = {98},
	number = {8},
	year = {2018},
	month = {AUG 28},
	abstract = {The recently demonstrated unconventional superconductivity [Cao et al., Nature (London) 556, 43 (2018)] in twisted bilayer graphene (tBLG) opens the possibility for interesting applications of two-dimensional layers that involve correlated electron states. Here we explore the possibility of modifying electronic correlations by the application of uniaxial pressure on the weakly interacting layers, which results in increased interlayer coupling and a modification of the magic angle value and associated density of states. Our findings are based on first-principles calculations that accurately describe the height-dependent interlayer coupling through the combined use of density functional theory and maximally localized Wannier functions. We obtain the relationship between twist angle and external pressure for the magic angle flat bands of tBLG. This may provide a convenient method to tune electron correlations by controlling the length scale of the superlattice.},
	issn = {2469-9950},
	doi = {10.1103/PhysRevB.98.085144},
	author = {Carr, Stephen and Fang, Shiang and Pablo Jarillo-Herrero and Efthimios Kaxiras}
}
@article { ISI:000433012900007,
	title = {Quantum plasmons with optical-range frequencies in doped few-layer graphene},
	journal = {PHYSICAL REVIEW B},
	volume = {97},
	number = {19},
	year = {2018},
	month = {MAY 21},
	abstract = {Although plasmon modes exist in doped graphene, the limited range of doping achieved by gating restricts the plasmon frequencies to a range that does not include the visible and infrared. Here we show, through the use of first-principles calculations, that the high levels of doping achieved by lithium intercalation in bilayer and trilayer graphene shift the plasmon frequencies into the visible range. To obtain physically meaningful results, we introduce a correction of the effect of plasmon interaction across the vacuum separating periodic images of the doped graphene layers, consisting of transparent boundary conditions in the direction perpendicular to the layers; this represents a significant improvement over the exact Coulomb cutoff technique employed in earlier works. The resulting plasmon modes are due to local field effects and the nonlocal response of the material to external electromagnetic fields, requiring a fully quantum mechanical treatment. We describe the features of these quantum plasmons, including the dispersion relation, losses, and field localization. Our findings point to a strategy for fine-tuning the plasmon frequencies in graphene and other two-dimensional materials.},
	issn = {2469-9950},
	doi = {10.1103/PhysRevB.97.195435},
	author = {Shirodkar, Sharmila N. and Marios Mattheakis and Cazeaux, Paul and Prineha Narang and Marin Soljacic and Efthimios Kaxiras}
}
@article { ISI:000440717600005,
	title = {Raman spectrum of CrI3: An ab initio study},
	journal = {PHYSICAL REVIEW B},
	volume = {98},
	number = {8},
	year = {2018},
	month = {AUG 3},
	abstract = {We study the Raman spectrum of CrI3, a material that exhibits magnetism in a single layer. We employ first-principles calculations within density functional theory to determine the effects of polarization, strain, and incident angle on the phonon spectra of the three-dimensional bulk and the single-layer two-dimensional structure, for both the high- and low-temperature crystal structures. Our results are in good agreement with existing experimental measurements and serve as a guide for additional investigations to elucidate the physics of this interesting material.},
	issn = {2469-9950},
	doi = {10.1103/PhysRevB.98.085406},
	author = {Larson, Daniel T. and Efthimios Kaxiras}
}
@article { ISI:000449723900049,
	title = {Reaction-Induced Excitations and Their Effect on Surface Chemistry},
	journal = {ACS CATALYSIS},
	volume = {8},
	number = {11},
	year = {2018},
	month = {NOV},
	pages = {10358-10363},
	abstract = {Despite intensive study of reactions on metals, it is unclear whether electronic excitations play an important role. Here, we show that nonadiabatic effects do indeed play a significant role in N-2 and H-2 dissociation on Ru nanoparticles. We employ nonadiabatic dynamical calculations based on realtime, time-dependent density functional theory to study energy dissipation during these exothermic reaction steps. We find that dissipation of the excess energy into excitation of electrons exceeds thermal dissipation into phonons. For isolated dissociation events, electronic friction can increase reaction barriers; furthermore, the excitations induced by a dissociation event can affect other reacting molecules. Our studies suggest that, for exothermic reactions, metal catalysts in reaction conditions may be constantly experiencing electronic excitations, and these excitations can significantly affect surface chemistry.},
	issn = {2155-5435},
	doi = {10.1021/acscatal.8b03266},
	author = {Montemore, Matthew M. and Robert Hoyt and Grigory Kolesov and Efthimios Kaxiras}
}
@article { ISI:000452322000001,
	title = {Relaxation and domain formation in incommensurate two-dimensional heterostructures},
	journal = {PHYSICAL REVIEW B},
	volume = {98},
	number = {22},
	year = {2018},
	month = {DEC 5},
	abstract = {We introduce configuration space as a natural representation for calculating the mechanical relaxation patterns of incommensurate two-dimensional (2D) bilayers. The approach can be applied to a wide variety of 2D materials through the use of a continuum model in combination with a generalized stacking fault energy for interlayer interactions. We present computational results for small-angle twisted bilayer graphene and molybdenum disulfide (MoS2), a representative material of the transition-metal dichalcogenide family of 2D semiconductors. We calculate accurate relaxations for MoS2 even at small twist-angle values, enabled by the fact that our approach does not rely on empirical atomistic potentials for interlayer coupling. The results demonstrate the efficiency of the configuration space method by computing relaxations with minimal computational cost. We also outline a general explanation of domain formation in 2D bilayers with nearly aligned lattices, taking advantage of the relationship between real space and configuration space. The configuration space approach also enables calculation of relaxations in incommensurate multilayer systems.},
	issn = {2469-9950},
	doi = {10.1103/PhysRevB.98.224102},
	author = {Carr, Stephen and Massatt, Daniel and Torrisi, Steven B. and Cazeaux, Paul and Luskin, Mitchell and Efthimios Kaxiras}
}
@article { ISI:000429103300032,
	title = {Unconventional superconductivity in magic-angle graphene superlattices},
	journal = {NATURE},
	volume = {556},
	number = {7699},
	year = {2018},
	month = {APR 5},
	pages = {43+},
	abstract = {The behaviour of strongly correlated materials, and in particular unconventional superconductors, has been studied extensively for decades, but is still not well understood. This lack of theoretical understanding has motivated the development of experimental techniques for studying such behaviour, such as using ultracold atom lattices to simulate quantum materials. Here we report the realization of intrinsic unconventional superconductivity-which cannot be explained by weak electron-phonon interactions-in a two-dimensional superlattice created by stacking two sheets of graphene that are twisted relative to each other by a small angle. For twist angles of about 1.1 degrees-the first {\textquoteleft}magic{\textquoteright} angle-the electronic band structure of this {\textquoteleft}twisted bilayer graphene{\textquoteright} exhibits flat bands near zero Fermi energy, resulting in correlated insulating states at half-filling. Upon electrostatic doping of the material away from these correlated insulating states, we observe tunable zero-resistance states with a critical temperature of up to 1.7 kelvin. The temperature-carrier-density phase diagram of twisted bilayer graphene is similar to that of copper oxides (or cuprates), and includes dome-shaped regions that correspond to superconductivity. Moreover, quantum oscillations in the longitudinal resistance of the material indicate the presence of small Fermi surfaces near the correlated insulating states, in analogy with underdoped cuprates. The relatively high superconducting critical temperature of twisted bilayer graphene, given such a small Fermi surface (which corresponds to a carrier density of about 1011 per square centimetre), puts it among the superconductors with the strongest pairing strength between electrons. Twisted bilayer graphene is a precisely tunable, purely carbon-based, two-dimensional superconductor. It is therefore an ideal material for investigations of strongly correlated phenomena, which could lead to insights into the physics of high-critical-temperature superconductors and quantum spin liquids.},
	issn = {0028-0836},
	doi = {10.1038/nature26160},
	author = {Cao, Yuan and Fatemi, Valla and Fang, Shiang and Kenji Watanabe and Takashi Taniguchi and Efthimios Kaxiras and Pablo Jarillo-Herrero}
}
@article { ISI:000423427400002,
	title = {Universal behavior of a dispersive Dirac cone in gradient-index plasmonic metamaterials},
	journal = {PHYSICAL REVIEW B},
	volume = {97},
	number = {3},
	year = {2018},
	month = {JAN 25},
	abstract = {We demonstrate analytically and numerically that the dispersive Dirac cone emulating an epsilon-near-zero (ENZ) behavior is a universal property within a family of plasmonic crystals consisting of two-dimensional (2D) metals. Our starting point is a periodic array of 2D metallic sheets embedded in an inhomogeneous and anisotropic dielectric host that allows for propagation of transverse-magnetic (TM) polarized waves. By invoking a systematic bifurcation argument for arbitrary dielectric profiles in one spatial dimension, we show how TM Bloch waves experience an effective dielectric function that averages out microscopic details of the host medium. The corresponding effective dispersion relation reduces to a Dirac cone when the conductivity of the metallic sheet and the period of the array satisfy a critical condition for ENZ behavior. Our analytical findings are in excellent agreement with numerical simulations.},
	issn = {2469-9950},
	doi = {10.1103/PhysRevB.97.035307},
	author = {Matthias Maier and Marios Mattheakis and Efthimios Kaxiras and Luskin, Mitchell and Dionisios Margetis}
}
@article { ISI:000423505500007,
	title = {Water facilitates oxygen migration on gold surfaces},
	journal = {PHYSICAL CHEMISTRY CHEMICAL PHYSICS},
	volume = {20},
	number = {4},
	year = {2018},
	month = {JAN 28},
	pages = {2196-2204},
	abstract = {The water-oxygen-gold interface is important in many surface processes and has potential influence on heterogeneous catalysis. Herein, it is shown that water facilitates the migration of atomic oxygen on Au(110), demonstrating the dynamic nature of surface adsorption. We demonstrate this effect for the first time, using in situ scanning tunnelling microscopy (STM), temperature-programmed reaction spectroscopy (TPRS) and first-principles theoretical calculations. The dynamic interaction of water with adsorbed O maintains a high dispersion of O on the surface, potentially creating reactive transient species. At low temperature and pressure, isotopic experiments show that adsorbed oxygen on the Au(110) surface exchanges with oxygen in (H2O)-O-18. The presence of water modulates local electronic properties and facilitates oxygen exchange. Combining experimental results and theory, we propose that hydroxyl is transiently formed via proton transfer from the water to adsorbed oxygen. Hydroxyl groups easily recombine to regenerate water and adsorbed oxygen atoms, the net result of which is migration of the adsorbed oxygen without significant change in its overall distribution on the surface. The presence of water creates a dynamic surface where mobile surface oxygen atoms and hydroxyls are present, which can lead to a better performance of gold catalysis in oxidation reactions.},
	issn = {1463-9076},
	doi = {10.1039/c7cp06451a},
	author = {Fang Xu and Ioanna Fampiou and O{\textquoteright}Connor, Christopher R. and Stavros Karakalos and Fanny Hiebel and Efthimios Kaxiras and Madix, Robert J. and Cynthia M. Friend}
}
@article {chen2017properties,
	title = {Properties of in-plane graphene/MoS2 heterojunctions},
	journal = {2D Materials},
	volume = {4},
	number = {4},
	year = {2017},
	pages = {045001},
	publisher = {IOP Publishing},
	doi = {10.1088/2053-1583/aa8313},
	author = {Chen, Wei and Yang, Yuan and Zhenyu Zhang and Efthimios Kaxiras}
}
@article {sensoy2017strain,
	title = {Strain effects on the behavior of isolated and paired sulfur vacancy defects in monolayer MoS 2},
	journal = {Physical Review B},
	volume = {95},
	number = {1},
	year = {2017},
	pages = {014106},
	publisher = {APS},
	doi = {10.1103/PhysRevB.95.014106},
	author = {Mehmet Gokhan Sensoy and Dmitry Vinichenko and Chen, Wei and Cynthia M. Friend and Efthimios Kaxiras}
}
@article { ISI:000404469000007,
	title = {Accurate formation energies of charged defects in solids: A systematic approach},
	journal = {PHYSICAL REVIEW B},
	volume = {95},
	number = {23},
	year = {2017},
	month = {JUN 30},
	abstract = {Defects on surfaces of semiconductors have a strong effect on their reactivity and catalytic properties. The concentration of different charge states of defects is determined by their formation energies. First-principles calculations are an important tool for computing defect formation energies and for studying the microscopic environment of the defect. The main problem associated with the widely used supercell method in these calculations is the error in the electrostatic energy, which is especially pronounced in calculations that involve surface slabs and two-dimensional materials. We present an internally consistent approach for calculating defect formation energies in inhomogeneous and anisotropic dielectric environments and demonstrate its applicability to the cases of the positively charged Cl vacancy on the NaCl (100) surface and the negatively charged S vacancy in monolayer MoS2.},
	issn = {2469-9950},
	doi = {10.1103/PhysRevB.95.235310},
	author = {Dmitry Vinichenko and Mehmet Gokhan Sensoy and Cynthia M. Friend and Efthimios Kaxiras}
}
@article { ISI:000430568502152,
	title = {Competition for active sites in steady state catalytic reactions; importance of weak van der Waals interactions},
	journal = {ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY},
	volume = {253},
	year = {2017},
	note = {253rd National Meeting of the American-Chemical-Society (ACS) on Advanced Materials, Technologies, Systems, and Processes, San Francisco, CA, APR 02-06, 2017},
	month = {APR 2},
	publisher = {Amer Chem Soc},
	issn = {0065-7727},
	author = {Robert Madix and Stavros Karakalos and Yunfei Xu and Tkatchenko, Alex and Kabeer, Fairoja and Chen, Wei and Efthimios Kaxiras and Cynthia Friend}
}
@article { ISI:000402773800027,
	title = {Effect of nanoscale flows on the surface structure of nanoporous catalysts},
	journal = {JOURNAL OF CHEMICAL PHYSICS},
	volume = {146},
	number = {21},
	year = {2017},
	month = {JUN 7},
	abstract = {The surface structure and composition of a multi-component catalyst are critical factors in determining its catalytic performance. The surface composition can depend on the local pressure of the reacting species, leading to the possibility that the flow through a nanoporous catalyst can affect its structure and reactivity. Here, we explore this possibility for oxidation reactions on nanoporous gold, an AgAu bimetallic catalyst. We use microscopy and digital reconstruction to obtain the morphology of a two-dimensional slice of a nanoporous gold sample. Using lattice Boltzmann fluid dynamics simulations along with thermodynamic models based on first-principles total-energy calculations, we show that some sections of this sample have low local O-2 partial pressures when exposed to reaction conditions, which leads to a pure Au surface in these regions, instead of the active bimetallic AgAu phase. We also explore the effect of temperature on the surface structure and find that moderate temperatures (approximate to 300-450 K) should result in the highest intrinsic catalytic performance, in apparent agreement with experimental results. Published by AIP Publishing.},
	issn = {0021-9606},
	doi = {10.1063/1.4984614},
	author = {Montemore, Matthew M. and Montessori, Andrea and Sauro Succi and Barroo, Cedric and Falcucci, Giacomo and Bell, David C. and Efthimios Kaxiras}
}
@article { ISI:000418955300018,
	title = {A force-matching Stillinger-Weber potential for MoS2: Parameterization and Fisher information theory based sensitivity analysis},
	journal = {JOURNAL OF APPLIED PHYSICS},
	volume = {122},
	number = {24},
	year = {2017},
	month = {DEC 28},
	abstract = {Two-dimensional molybdenum disulfide (MoS2) is a promising material for the next generation of switchable transistors and photodetectors. In order to perform large-scale molecular simulations of the mechanical and thermal behavior of MoS2-based devices, an accurate interatomic potential is required. To this end, we have developed a Stillinger-Weber potential for monolayer MoS2. The potential parameters are optimized to reproduce the geometry (bond lengths and bond angles) of MoS2 in its equilibrium state and to match as closely as possible the forces acting on the atoms along a dynamical trajectory obtained from ab initio molecular dynamics. Verification calculations indicate that the new potential accurately predicts important material properties including the strain dependence of the cohesive energy, the elastic constants, and the linear thermal expansion coefficient. The uncertainty in the potential parameters is determined using a Fisher information theory analysis. It is found that the parameters are fully identified, and none are redundant. In addition, the Fisher information matrix provides uncertainty bounds for predictions of the potential for new properties. As an example, bounds on the average vibrational thickness of a MoS2 monolayer at finite temperature are computed and found to be consistent with the results from a molecular dynamics simulation. The new potential is available through the OpenKIM interatomic potential repository at https://openkim.org/cite/MO\_201919462778\_000. Published by AIP Publishing.},
	issn = {0021-8979},
	doi = {10.1063/1.5007842},
	author = {Wen, Mingjian and Shirodkar, Sharmila N. and Plechac, Petr and Efthimios Kaxiras and Elliott, Ryan S. and Tadmor, Ellad B.}
}
@article { ISI:000430568502339,
	title = {Heterogeneous photochemical processes on metal oxides},
	journal = {ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY},
	volume = {253},
	year = {2017},
	note = {253rd National Meeting of the American-Chemical-Society (ACS) on Advanced Materials, Technologies, Systems, and Processes, San Francisco, CA, APR 02-06, 2017},
	month = {APR 2},
	publisher = {Amer Chem Soc},
	issn = {0065-7727},
	author = {Crampton, Andrew and Fang Xu and Efthimios Kaxiras and Cai, Lili and Zheng, Xiaolin and Cynthia Friend}
}
@article { ISI:000412730300008,
	title = {Impact of Vibrations and Electronic Coherence on Electron Transfer in Flat Molecular Wires},
	journal = {MRS ADVANCES},
	volume = {2},
	number = {14},
	year = {2017},
	pages = {811-816},
	abstract = {Electron transfer in molecular wires are of fundamental importance for a range of optoelectronic applications. The impact of electronic coherence and ionic vibrations on transmittance are of great importance to determine the mechanisms, and subsequently the type of wires that are most promising for applications. In this work, we use the real-time formulation of time-dependent density functional theory to study electron transfer through oligo-pphenylenevinylene (OPV) and the recently synthesized carbon bridged counterpart (COPV). A system prototypical of organic photovoltaics is setup by bridging a porphyrin-fullerene dyad, allowing a photo-excited electron to flow between the Zn-porphyrin (ZnP) chromophore and the C60 electron acceptor through the molecular wire. The excited state is described using the fully self-consistent.-SCF method. The state is then propagated in time using the real-time TD-DFT scheme, while describing ionic vibrations with classical nuclei. The charge transferred between porphyrin and C60 is calculated and correlated with the velocity autocorrelation functions of the ions. This provides a microscopic insight to vibrational and tunneling contributions to electron transport in linked porphyrin-fullerene dyads. We elaborate on important details in describing the excited state and trajectory sampling.},
	issn = {2059-8521},
	doi = {10.1557/adv.2017.157},
	author = {Granas, Oscar and Grigory Kolesov and Efthimios Kaxiras}
}
@article { ISI:000396295800036,
	title = {Macroscopic 3D Nanoporosity Formation by Dry Oxidation of AgAu Alloys},
	journal = {JOURNAL OF PHYSICAL CHEMISTRY C},
	volume = {121},
	number = {9},
	year = {2017},
	month = {MAR 9},
	pages = {5115-5122},
	abstract = {3D nanoporous metals made by alloy corrosion have attracted much attention due to various promising applications ranging from catalysis and sensing to energy storage and actuation. In this work we report a new process for the fabrication of 3D open nanoporous metal networks that phenomenologically resembles the nano-Kirkendall hollowing process previously reported for Ag/Au nanowires and nano particles, with the difference that the involved length scales are 10-100 times larger. Specifically, we find that dry oxidation of Ag70Au30 bulk alloy samples by ozone exposure at 150 C-omicron stimulates extremely rapid Ag outward diffusion toward the gas/alloy-surface interface, at rates at least 5 orders of magnitude faster than predicted on the basis of reported Ag bulk diffusion values. The micrometer-thick Ag depleted alloy region thus formed transforms into a 3D open nanoporous network morphology upon further exposure to methanol-O-2 at 150 C-omicron. These findings have important implications for practical applications of alloys, for example as catalysts, by demonstrating that large-scale compositional and morphological changes can be triggered by surface chemical reactions at low temperatures, and that dilute alloys such as Au97Ag3 are more resilient against such changes.},
	issn = {1932-7447},
	doi = {10.1021/acs.jpcc.6b12847},
	author = {Barroo, Cedric and Montemore, Matthew M. and Janvelyan, Nare and Zugic, Branko and Akey, Austin J. and Magyar, Andrew P. and Ye, Jianchao and Efthimios Kaxiras and Biener, Juergen and Bell, David C.}
}
@article { ISI:000393183100040,
	title = {Magnetic resonance spectroscopy of an atomically thin material using a single-spin qubit},
	journal = {SCIENCE},
	volume = {355},
	number = {6324},
	year = {2017},
	month = {FEB 3},
	pages = {503+},
	abstract = {Two-dimensional (2D) materials offer a promising platform for exploring condensed matter phenomena and developing technological applications. However, the reduction of material dimensions to the atomic scale poses a challenge for traditional measurement and interfacing techniques that typically couple to macroscopic observables. We demonstrate a method for probing the properties of 2D materials via nanometer-scale nuclear quadrupole resonance (NQR) spectroscopy using individual atomlike impurities in diamond. Coherent manipulation of shallow nitrogen-vacancy (NV) color centers enables the probing of nanoscale ensembles down to approximately 30 nuclear spins in atomically thin hexagonal boron nitride (h-BN). The characterization of low-dimensional nanoscale materials could enable the development of new quantum hybrid systems, combining atomlike systems coherently coupled with individual atoms in 2D materials.},
	issn = {0036-8075},
	doi = {10.1126/science.aal2538},
	author = {I. Lovchinsky and Sanchez-Yamagishi, J. D. and Urbach, E. K. and Choi, S. and Fang, S. and T. I. Andersen and K. Watanabe and T. Taniguchi and A. Bylinskii and E. Kaxiras and P. Kim and H. Park and M. D. Lukin}
}
@article { ISI:000434984500003,
	title = {Manipulating polarized light with a planar slab of black phosphorus},
	journal = {JOURNAL OF PHYSICS COMMUNICATIONS},
	volume = {1},
	number = {4},
	year = {2017},
	month = {NOV},
	abstract = {Wave polarization contains valuable information for electromagnetic signal processing; thus, the ability to manipulate it, can be extremely useful in modeling photonic devices. In this work, we propose designs comprised of one of the emerging and interesting media: black phosphorus (BP). Due to substantial in-plane anisotropy, a single slab of BP can be very efficient for controlling the polarization state of electromagnetic waves. We investigate BP slabs that filter the fields along one direction, or achieve polarization axis rotation, or convert linear polarization to circular. These slabs can be employed as components in numerous mid-IR integrated structures.},
	issn = {2399-6528},
	doi = {10.1088/2399-6528/aa90c8},
	author = {Constantinos A. Valagiannopoulos and Marios Mattheakis and Shirodkar, Sharmila N. and Efthimios Kaxiras}
}
@article { ISI:000413848300007,
	title = {Nanoribbon edges of transition-metal dichalcogenides: Stability and electronic properties},
	journal = {PHYSICAL REVIEW B},
	volume = {96},
	number = {16},
	year = {2017},
	month = {OCT 27},
	abstract = {Nanoribbons of molybdenum disulfide (MoS2) are interesting one-dimensional (1D) nanostructures with intriguing electronic properties, consisting of a semiconducting bulk bounded by edges with metallic character. Edges of similar character can also be expected in other transition-metal dichalcogenide (TMDC) nanostructures. We report first-principles electronic structure calculations for the total energy and the band structure of four representative TMDCs, MoS2, MoSe2, WS2, WSe2, in various 1D nanoribbon configurations. We compare the thermodynamic stability and the electronic structure of the 2D bulk and 35 different quasi-1D nanoribbons for each of the four materials. In each case, we consider the reconstructions of the zigzag metal-terminated edge by adding different amounts of chalcogen adatoms. The 1D structures we investigated have positive edge energies when the chalcogen chemical potential is close to the energy of the bulk chalcogen phase, and negative edge energies for higher chemical potential values. We find that the reconstruction with two chalcogen adatoms per edge metal atom is the most stable under usual experimental conditions and that all 1D nanoribbon structures exhibit metallic character.},
	issn = {2469-9950},
	doi = {10.1103/PhysRevB.96.165436},
	author = {Davelou, Daphne and Kopidakis, Georgios and Efthimios Kaxiras and Remediakis, Ioannis N.}
}
@article { ISI:000416429000002,
	title = {Polaron-induced phonon localization and stiffening in rutile TiO2},
	journal = {PHYSICAL REVIEW B},
	volume = {96},
	number = {19},
	year = {2017},
	month = {NOV 29},
	abstract = {Small polaron formation in transition metal oxides, like the prototypical material rutile TiO2, remains a puzzle and a challenge to simple theoretical treatment. In our combined experimental and theoretical study, we examine this problem using Raman spectroscopy of photoexcited samples and real-time time-dependent density functional theory (RT-TDDFT), which employs Ehrenfest dynamics to couple the electronic and ionic subsystems. We observe experimentally the unexpected stiffening of the A(1g) phonon mode under UV illumination and provide a theoretical explanation for this effect. Our analysis also reveals a possible reason for the observed anomalous temperature dependence of the Hall mobility. Small polaron formation in rutile TiO2 is a strongly nonadiabatic process and is adequately described by Ehrenfest dynamics at time scales of polaron formation.},
	issn = {2469-9950},
	doi = {10.1103/PhysRevB.96.195165},
	author = {Grigory Kolesov and Kolesov, Boris A. and Efthimios Kaxiras}
}
@article { ISI:000392035500064,
	title = {Polyiodide-Doped Graphene},
	journal = {JOURNAL OF PHYSICAL CHEMISTRY C},
	volume = {121},
	number = {1},
	year = {2017},
	month = {JAN 12},
	pages = {609-615},
	abstract = {Iodine-doped graphene has recently attracted significant interest as a result of its enhanced conductivity and improved catalytic activity. Using density functional theory calculations, we obtain the formation energy, desorption rate, and electronic properties for graphene systems doped with polyiodide chains consisting of 1-6 iodine atoms in the low-concentration limit. We find that I-3 and I-5 act as p-type surface dopants that shift the Fermi level 0.46 and 0.57 eV below the Dirac point, respectively. For these two molecules, molecular orbital theory and analysis of the charge density show that doping transfers electronic charge to iodine pi* molecular orbitals oriented perpendicular to the graphene sheet. For even-length polyiodides, we find that I-6 and I-4 decompose to I-2, which readily desorbs at 300 K. Adsorption energy calculations further show that I-3 acts as an effective catalyst for the oxygen reduction reaction on graphene by stabilizing the rate-limiting OOH intermediate.},
	issn = {1932-7447},
	doi = {10.1021/acs.jpcc.6b11653},
	author = {Hoyt, Robert A. and E. Marielle Remillard and Ekin D. Cubuk and Chad D. Vecitis and Efthimios Kaxiras}
}
@article { ISI:000407974000001,
	title = {Properties of in-plane graphene/MoS2 heterojunctions},
	journal = {2D MATERIALS},
	volume = {4},
	number = {4},
	year = {2017},
	month = {DEC},
	abstract = {The graphene/MoS2 heterojunction formed by joining the two components laterally in a single plane promises to exhibit a low-resistance contact according to the Schottky-Mott rule. Here we provide an atomic-scale description of the structural, electronic, and magnetic properties of this type of junction. We first identify the energetically favorable structures in which the preference of forming C-S or C-Mo bonds at the boundary depends on the chemical conditions. We find that significant non-carrier related charge transfer between graphene and undoped MoS2 is localized at the boundary. We show that the abundant 1D boundary states substantially pin the Fermi level in the lateral contact between graphene and MoS2, in close analogy to the effect of 2D interfacial states in the contacts between 3D materials. Furthermore, we propose specific ways in which these effects can be exploited to achieve spin-polarized currents.},
	issn = {2053-1583},
	doi = {10.1088/2053-1583/aa8313},
	author = {Chen, Wei and Yang, Yuan and Zhenyu Zhang and Efthimios Kaxiras}
}
@article { ISI:000391439300036,
	title = {Relationship between local structure and relaxation in out-of-equilibrium glassy systems},
	journal = {PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA},
	volume = {114},
	number = {2},
	year = {2017},
	month = {JAN 10},
	pages = {263-267},
	abstract = {The dynamical glass transition is typically taken to be the temperature at which a glassy liquid is no longer able to equilibrate on experimental timescales. Consequently, the physical properties of these systems just above or below the dynamical glass transition, such as viscosity, can change by many orders of magnitude over long periods of time following external perturbation. During this progress toward equilibrium, glassy systems exhibit a history dependence that has complicated their study. In previous work, we bridged the gap between structure and dynamics in glassy liquids above their dynamical glass transition temperatures by introducing a scalar field called {\textquoteleft}{\textquoteleft}softness,{\textquoteright}{\textquoteright} a quantity obtained using machine-learning methods. Softness is designed to capture the hidden patterns in relative particle positions that correlate strongly with dynamical rearrangements of particle positions. Here we show that the out-of-equilibrium behavior of a model glass-forming system can be understood in terms of softness. To do this we first demonstrate that the evolution of behavior following a temperature quench is a primarily structural phenomenon: The structure changes considerably, but the relationship between structure and dynamics remains invariant. We then show that the relaxation time can be robustly computed from structure as quantified by softness, with the same relation holding both in equilibrium and as the system ages. Together, these results show that the history dependence of the relaxation time in glasses requires knowledge only of the softness in addition to the usual state variables.},
	issn = {0027-8424},
	doi = {10.1073/pnas.1610204114},
	author = {Schoenholz, Samuel S. and Ekin D. Cubuk and Efthimios Kaxiras and Liu, Andrea J.}
}
@article { ISI:000405669900006,
	title = {Representations in neural network based empirical potentials},
	journal = {JOURNAL OF CHEMICAL PHYSICS},
	volume = {147},
	number = {2},
	year = {2017},
	month = {JUL 14},
	abstract = {Many structural and mechanical properties of crystals, glasses, and biological macromolecules can be modeled from the local interactions between atoms. These interactions ultimately derive from the quantum nature of electrons, which can be prohibitively expensive to simulate. Machine learning has the potential to revolutionize materials modeling due to its ability to efficiently approximate complex functions. For example, neural networks can be trained to reproduce results of density functional theory calculations at a much lower cost. However, how neural networks reach their predictions is not well understood, which has led to them being used as a {\textquoteleft}{\textquoteleft}black box{\textquoteright}{\textquoteright} tool. This lack of understanding is not desirable especially for applications of neural networks in scientific inquiry. We argue that machine learning models trained on physical systems can be used as more than just approximations since they had to {\textquoteleft}{\textquoteleft}learn{\textquoteright}{\textquoteright} physical concepts in order to reproduce the labels they were trained on. We use dimensionality reduction techniques to study in detail the representation of silicon atoms at different stages in a neural network, which provides insight into how a neural network learns to model atomic interactions. Published by AIP Publishing.},
	issn = {0021-9606},
	doi = {10.1063/1.4990503},
	author = {Ekin D. Cubuk and Malone, Brad D. and Onat, Berk and Amos Waterland and Efthimios Kaxiras}
}
@article { ISI:000392277000001,
	title = {Strain effects on the behavior of isolated and paired sulfur vacancy defects in monolayer MoS2},
	journal = {PHYSICAL REVIEW B},
	volume = {95},
	number = {1},
	year = {2017},
	month = {JAN 17},
	abstract = {We investigate the behavior of sulfur vacancy defects, the most abundant type of intrinsic defect in monolayer MoS2, using first-principles calculations based on density functional theory. We consider the dependence of the isolated defect formation energy on the charge state and on uniaxial tensile and compressive strain up to 5\%. We also consider the possibility of defect clustering by examining the formation energies of pairs of vacancies at various relative positions, and their dependence on charge state and strain. We find that there is no driving force for vacancy clustering, independent of strain in the material. The barrier for diffusion of S vacancies is larger than 1.9 eV in both charged and neutral states regardless of the presence of other nearby vacancies. We conclude that the formation of extended defects from S vacancies in planar monolayer MoS2 is hindered both thermodynamically and kinetically.},
	issn = {2469-9950},
	doi = {10.1103/PhysRevB.95.014106},
	author = {Mehmet Gokhan Sensoy and Dmitry Vinichenko and Chen, Wei and Cynthia M. Friend and Efthimios Kaxiras}
}
@article { ISI:000394368000003,
	title = {Twistronics: Manipulating the electronic properties of two-dimensional layered structures through their twist angle},
	journal = {PHYSICAL REVIEW B},
	volume = {95},
	number = {7},
	year = {2017},
	month = {FEB 17},
	abstract = {The ability in experiments to control the relative twist angle between successive layers in two-dimensional (2D) materials offers an approach to manipulating their electronic properties; we refer to this approach as {\textquoteleft}{\textquoteleft}twistronics.{\textquoteright}{\textquoteright} A major challenge to theory is that, for arbitrary twist angles, the resulting structure involves incommensurate (aperiodic) 2D lattices. Here, we present a general method for the calculation of the electronic density of states of aperiodic 2D layered materials, using parameter-free Hamiltonians derived from ab initio density-functional theory. We use graphene, a semimetal, and MoS2, a representative of the transition-metal dichalcogenide family of 2D semiconductors, to illustrate the application of our method, which enables fast and efficient simulation of multilayered stacks in the presence of local disorder and external fields. We comment on the interesting features of their density of states as a function of twist angle and local configuration and on how these features can be experimentally observed.},
	issn = {2469-9950},
	doi = {10.1103/PhysRevB.95.075420},
	author = {Carr, Stephen and Massatt, Daniel and Fang, Shiang and Cazeaux, Paul and Luskin, Mitchell and Efthimios Kaxiras}
}
@article { ISI:000372413700001,
	title = {Bounds on nanoscale nematicity in single-layer FeSe/SrTiO3},
	journal = {PHYSICAL REVIEW B},
	volume = {93},
	number = {12},
	year = {2016},
	month = {MAR 18},
	abstract = {We use scanning tunneling microscopy (STM) and quasiparticle interference (QPI) imaging to investigate the low-energy orbital texture of single-layer FeSe/SrTiO3. We develop a T-matrix model of multiorbital QPI to disentangle scattering intensities from Fe 3d(xz) and 3d(yz) bands, enabling the use of STM as a nanoscale detection tool of nematicity. By sampling multiple spatial regions of a single-layer FeSe/SrTiO3 film, we quantitatively exclude static xz/yz orbital ordering with domain size larger than delta r(2) = 20 nm x 20 nm, xz/yz Fermi wave vector difference larger than delta k = 0.014 pi, and energy splitting larger than delta E = 3.5 meV. The lack of detectable ordering pinned around defects places qualitative constraints on models of fluctuating nematicity.},
	issn = {2469-9950},
	doi = {10.1103/PhysRevB.93.125129},
	author = {Huang, Dennis and Webb, Tatiana A. and Fang, Shiang and Song, Can-Li and Chang, Cui-Zu and Moodera, Jagadeesh S. and Efthimios Kaxiras and Hoffman, Jennifer E.}
}
@article { ISI:000368067200002,
	title = {Catalyst design for enhanced sustainability through fundamental surface chemistry},
	journal = {PHILOSOPHICAL TRANSACTIONS OF THE ROYAL SOCIETY A-MATHEMATICAL PHYSICAL AND ENGINEERING SCIENCES},
	volume = {374},
	number = {2061},
	year = {2016},
	month = {FEB 28},
	abstract = {Decreasing energy consumption in the production of platform chemicals is necessary to improve the sustainability of the chemical industry, which is the largest consumer of delivered energy. The majority of industrial chemical transformations rely on catalysts, and therefore designing new materials that catalyse the production of important chemicals via more selective and energy-efficient processes is a promising pathway to reducing energy use by the chemical industry. Efficiently designing new catalysts benefits from an integrated approach involving fundamental experimental studies and theoretical modelling in addition to evaluation of materials under working catalytic conditions. In this review, we outline this approach in the context of a particular catalyst-nanoporous gold (npAu)-which is an unsupported, dilute AgAu alloy catalyst that is highly active for the selective oxidative transformation of alcohols. Fundamental surface science studies on Au single crystals and AgAu thin-film alloys in combination with theoretical modelling were used to identify the principles which define the reactivity of npAu and subsequently enabled prediction of new reactive pathways on this material. Specifically, weak van der Waals interactions are key to the selectivity of Au materials, including npAu. We also briefly describe other systems in which this integrated approach was applied.},
	issn = {1364-503X},
	doi = {10.1098/rsta.2015.0077},
	author = {Personick, Michelle L. and Montemore, Matthew M. and Efthimios Kaxiras and Madix, Robert J. and Biener, Juergen and Cynthia M. Friend}
}
@article { ISI:000385175000053,
	title = {Controlling O coverage and stability by alloying Au and Ag},
	journal = {PHYSICAL CHEMISTRY CHEMICAL PHYSICS},
	volume = {18},
	number = {38},
	year = {2016},
	month = {OCT 14},
	pages = {26844-26853},
	abstract = {One of the most critical factors in oxidation catalysis is controlling the state of oxygen on the surface. Au and Ag are both effective selective oxidation catalysts for various reactions, and their interactions with oxygen are critical for determining their catalytic performance. Here, we show that the state of oxygen on a catalytic surface can be controlled by alloying Au and Ag. Using temperature programmed desorption, density functional theory (DFT), and Monte Carlo simulations, we examine how alloying Au into an Ag(110) surface affects O-2 dissociation, O coverage, and O stability. DFT calculations indicate that Au resides in the second layer, in agreement with previous experimental findings. The minimum ensemble size for O-2 dissociation is 2 Ag atoms in adjacent rows of the second layer. Surprisingly, adsorbed O-2 and the dissociation transition state interact directly with metal atoms in the adjacent trough, such that Au in this position inhibits O-2 dissociation by direct repulsion with oxygen electronic states. Using Monte Carlo simulations based on DFT energetics, we create models of the surface that agree closely with our experimental results. Both show that the O-2 uptake decreases nearly linearly as the Au concentration increases, and no O-2 uptake occurs for Au concentrations above 50\%. For Au concentrations greater than 18\%, increasing the Au concentration also decreases the stability of the adsorbed O. Based on these results, the O coverage and O stability can be tuned, in some cases independently. We also study how the reactivity of the surface is affected by these factors using CO2 oxidation as a simple test reaction.},
	issn = {1463-9076},
	doi = {10.1039/c6cp05611c},
	author = {Montemore, Matthew M. and Ekin D. Cubuk and Klobas, J. Eric and Schmid, Martin and Madix, Robert J. and Cynthia M. Friend and Efthimios Kaxiras}
}
@article { ISI:000431905705455,
	title = {Design principles for sustainable catalysis from fundamental surface chemistry},
	journal = {ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY},
	volume = {251},
	year = {2016},
	month = {MAR 13},
	issn = {0065-7727},
	author = {Cynthia Friend and Stavros Karakalos and Fanny Hiebel and Yunfei Xu and Chen, Wei and Kabeer, Fairoja and Montemore, Matthew and Zugic, Branko and Biener, Juergen and Alexandre Tkatchenko and Efthimios Kaxiras and Robert Madix}
}
@article { ISI:000377837800003,
	title = {Direct visualization of quasi-ordered oxygen chain structures on Au(110)-(1 x 2)},
	journal = {SURFACE SCIENCE},
	volume = {650},
	number = {SI},
	year = {2016},
	month = {AUG},
	pages = {5-10},
	abstract = {The Au(110) surface offers unique advantages for atomically-resolved model studies of catalytic oxidation processes on gold. We investigate the adsorption of oxygen on Au(110) using a combination of scanning tunneling microscopy (STM) and density functional theory (DFT) methods. We identify the typical (empty-states) STM contrast resulting from adsorbed oxygen as atomic-sized dark features of electronic origin. DFT-based image simulations confirm that chemisorbed oxygen is generally detected indirectly, from the binding -induced electronic structure modification of gold. STM images show that adsorption occurs without affecting the general structure of the pristine Au(110) missing-row reconstruction. The tendency to form one-dimensional structures is observed already at low coverage (,
	issn = {0039-6028},
	doi = {10.1016/j.susc.2015.09.018},
	author = {Hiebel, F. and Montemore, M. M. and E. Kaxiras and C.M. Friend}
}
@article { ISI:000370794600003,
	title = {Dual role of Fe dopants in enhancing stability and charge transfer in (Li0.8Fe0.2)OHFeSe superconductors},
	journal = {PHYSICAL REVIEW B},
	volume = {93},
	number = {6},
	year = {2016},
	month = {FEB 25},
	abstract = {The recently discovered (Li0.8Fe0.2)OHFeSe superconductor provides a new platform for exploiting the microscopic mechanisms of high-T-c superconductivity in FeSe-derived systems. Using density functional theory calculations, we first show that substitution of Li by Fe not only significantly strengthens the attraction between the (Li0.8Fe0.2)OH spacing layers and the FeSe superconducting layers along the c axis but also minimizes the lattice mismatch between the two in the ab plane, both favorable for stabilizing the overall structure. Next, we explore the electron injection into FeSe from the spacing layers and unambiguously identify the Fe-0.2 components to be the origin of the dramatically enhanced interlayer charge transfer. We further reveal that the system strongly favors collinear antiferromagnetic ordering in the FeSe layers, but the spacing layers can be either antiferromagnetic or ferromagnetic depending on the Fe-0.2 spatial distribution. Based on these insights, we predict (Li0.8Co0.2)OHFeSe to be structurally stable with even larger electron injection and potentially higher T-c.},
	issn = {2469-9950},
	doi = {10.1103/PhysRevB.93.064517},
	author = {Chen, Wei and Zeng, Changgan and Efthimios Kaxiras and Zhenyu Zhang}
}
@article { ISI:000379794200037,
	title = {Dumbbell Defects in FeSe Films: A Scanning Tunneling Microscopy and First-Principles Investigation},
	journal = {NANO LETTERS},
	volume = {16},
	number = {7},
	year = {2016},
	month = {JUL},
	pages = {4224-4229},
	abstract = {The properties of iron-based superconductors (Fe-SCs) can be varied dramatically with the introduction of dopants and atomic defects. As a pressing example, FeSe, parent phase of the highest-T-c Fe-SC, exhibits prevalent defects with atomic-scale {\textquoteleft}{\textquoteleft}dumbbell{\textquoteright}{\textquoteright} signatures as imaged by scanning tunneling microscopy (STM). These defects spoil superconductivity when their concentration exceeds 2.5\%. Resolving their chemical identity is a prerequisite to applications such as nanoscale patterning of superconducting/nonsuperconducting regions in FeSe as well as fundamental questions such as the mechanism of superconductivity and the path by which the defects destroy it. We use STM and density functional theory to characterize and identify the dumbbell defects. In contrast to previous speculations about Se adsorbates or substitutions, we find that an Fe-site vacancy is the most energetically favorable defect in Se-rich conditions and reproduces our observed STM signature. Our calculations shed light more generally on the nature of Se capping, the removal of Fe vacancies via annealing, and their ordering into a root 5 x root 5 superstructure in FeSe and related alkali-doped compounds.},
	issn = {1530-6984},
	doi = {10.1021/acs.nanolett.6b01163},
	author = {Huang, Dennis and Webb, Tatiana A. and Song, Can-Li and Chang, Cui-Zu and Moodera, Jagadeesh S. and Efthimios Kaxiras and Hoffinan, Jennifer E.}
}
@article { ISI:000383570900003,
	title = {The effect of Ag, Pb and Bi impurities on grain boundary sliding and intergranular decohesion in Copper},
	journal = {PHILOSOPHICAL MAGAZINE},
	volume = {96},
	number = {27, A},
	year = {2016},
	pages = {2868-2886},
	abstract = {We investigate the changes in grain boundary sliding (GBS) and intergranular decohesion in copper (Cu), due to the inclusion of bismuth (Bi), lead (Pb) and silver (Ag) substitutional impurity atoms at a Sigma 5 (012) symmetric tilt grain boundary (GB), using a first-principles concurrent multiscale approach. We first study the segregation behavior of the impurities by determining the impurity segregation energy in the vicinity of the GB. We find that the energetically preferred sites are on the GB plane. We investigate the intergranular decohesion of Cu by Bi and Pb impurities and compare this to the effect of Ag impurities by considering the work of separation, Ws and the tensile strength, st. Both Ws and st decrease in the presence of Bi and Pb impurities, indicating their great propensity for intergranular embrittlement, whilst the presence of Ag impurities has only a small effect. We consider GBS to assess the mechanical properties in nanocrystalline metals and find that all three impurities strongly inhibit GBS, with Ag having the biggest effect. This suggests that Ag has a strong effect on the mechanical properties of nanocrystalline Cu, even though its effect on the intergranular decohesion properties of coarse-grained Cu is not significant.},
	issn = {1478-6435},
	doi = {10.1080/14786435.2016.1217360},
	author = {Georg Schusteritsch and Kuehne, Thomas D. and Guo, Zheng Xiao and Efthimios Kaxiras}
}
@article { ISI:000390625800009,
	title = {Effects of Knudsen diffusivity on the effective reactivity Of nanoporous catalyst media},
	journal = {JOURNAL OF COMPUTATIONAL SCIENCE},
	volume = {17},
	number = {2, SI},
	year = {2016},
	note = {24th International Conference on Discrete Simulation of Fluid Dynamics (DSFD), Royal Soc Edinburgh, Edinburgh, SCOTLAND, JUL 13-17, 2015},
	month = {NOV},
	pages = {377-383},
	abstract = {We investigate the non-equilibrium hydrodynamic effects on the reactivity of a nanoporous catalytic sample. Numerical simulations using the Lattice Boltzmann Method (LBM) show that non-equilibrium effects enhance the reactivity of the porous sample, in agreement with theoretical predictions [1]. In addition, we provide a quantitative assessment of the reactivity in terms of the thickness of the reactive layer inside the nanoporous catalytic sample. Such an assessment constitutes a first step towards integrated simulations encompassing nanoscale reactivity and transport coefficients within a macroscale description of experimental relevance. (C) 2016 Elsevier B.V. All rights reserved.},
	issn = {1877-7503},
	doi = {10.1016/j.jocs.2016.04.006},
	author = {Montessori, A. and Prestininzi, P. and La Rocca, M. and Falcucci, G. and S. Succi and E. Kaxiras}
}
@article { ISI:000396236400003,
	title = {Electric field tuning of band offsets in transition metal dichalcogenides},
	journal = {PHYSICAL REVIEW B},
	volume = {94},
	number = {24},
	year = {2016},
	month = {DEC 21},
	abstract = {We use first-principles calculations to investigate the band structure evolution of WX2/MoX2 (X = S, Se) heterobilayers under a perpendicular electric field. We characterize the extent to which the type II band alignment in these compounds can be tuned or inverted electrostatically. Our results demonstrate two effects of the stacking configuration. First, different stackings produce different net dipole moments, resulting in band offset variations that are larger than 0.1 eV. Second, based on symmetry constraints that depend on stacking, a perpendicular electric field may hybridizeWX(2) and MoX2 bands that cross at the Brillouin zone corner K. Our results suggest that external electric fields can be used to tune the physics of intralayer and interlayer excitons in heterobilayers of transition metal dichalcogenides.},
	issn = {2469-9950},
	doi = {10.1103/PhysRevB.94.241303},
	author = {Huang, Dennis and Efthimios Kaxiras}
}
@article { ISI:000378813800004,
	title = {Electronic structure theory of weakly interacting bilayers},
	journal = {PHYSICAL REVIEW B},
	volume = {93},
	number = {23},
	year = {2016},
	month = {JUN 27},
	abstract = {We derive electronic structure models for weakly interacting bilayers such as graphene-graphene and graphene-hexagonal boron nitride, based on density functional theory calculations followed by Wannier transformation of electronic states. These transferable interlayer coupling models can be applied to investigate the physics of bilayers with arbitrary translations and twists. The functional form, in addition to the dependence on the distance, includes the angular dependence that results from higher angular momentum components in the Wannier p(z) orbitals. We demonstrate the capabilities of the method by applying it to a rotated graphene bilayer, which produces the analytically predicted renormalization of the Fermi velocity, Van Hove singularities in the density of states, and moire pattern of the electronic localization at small twist angles. We further extend the theory to obtain the effective couplings by integrating out neighboring layers. This approach is instrumental for the design of van der Walls heterostructures with desirable electronic features and transport properties and for the derivation of low-energy theories for graphene stacks, including proximity effects from other layers.},
	issn = {2469-9950},
	doi = {10.1103/PhysRevB.93.235153},
	author = {Fang, Shiang and Efthimios Kaxiras}
}
@article { ISI:000385469800013,
	title = {Enhancing the Hydrogen Activation Reactivity of Nonprecious Metal Substrates via Confined Catalysis Underneath Graphene},
	journal = {NANO LETTERS},
	volume = {16},
	number = {10},
	year = {2016},
	month = {OCT},
	pages = {6058-6063},
	abstract = {In the hydrogen evolution reaction (HER), the reactivity as a function of the hydrogen adsorption energy on different metal substrates follows a well-known;volcano curve, peaked a the precious inetal Pt. The goal. of turning nonprecious metals into efficient catalysts for HER and other important chemical reactions is a :fundamental challenge; it is-also of technological significance. Here, we present results toward, achieving Ihis goal by exploiting the synergistic power of marginal catalysis and confined catalysis. Using density functional theory calculations, we first show that the volcano curve stays qualitatively intact when van der Waals attractions between a hydrogen adatom and different metal (111) surfaces are included. We further show that the hydrogen adsorption:energy on the metal: surfaces is weakened by 0.11-0.23 eV when hydrogen is confinedbetween graphene and the metal surfaces, with Ni exhibiting the largest change. Inparticular, we find that the graphene-modified volcano curve peaks around Ni, whose bare surface already possesses moderate (or :marginal) reactivity,i and the corresponding HER rate of grapllene-covered comparable to that of bare Pt. A hydrogen adatom has high mobility within the confined geometry. These findings demonstrate that graphene-coyeted Ni is an appealing effective stable, and economical catalytic platform for HER.},
	issn = {1530-6984},
	doi = {10.1021/acs.nanolett.6b02052},
	author = {Zhou, Yinong and Chen, Wei and Ping Cui and Zeng, Jiang and Lin, Zhuonan and Efthimios Kaxiras and Zhenyu Zhang}
}
@article { ISI:000387538400002,
	title = {Epsilon-near-zero behavior from plasmonic Dirac point: Theory and realization using two-dimensional materials},
	journal = {PHYSICAL REVIEW B},
	volume = {94},
	number = {20},
	year = {2016},
	month = {NOV 10},
	abstract = {The electromagnetic response of a two-dimensional metal embedded in a periodic array of a dielectric host can give rise to a plasmonic Dirac point that emulates epsilon-near-zero (ENZ) behavior. This theoretical result is extremely sensitive to structural features like periodicity of the dielectric medium and thickness imperfections. We propose that such a device can actually be realized by using graphene as the two-dimensional metal and materials like the layered semiconducting transition-metal dichalcogenides or hexagonal boron nitride as the dielectric host. We propose a systematic approach, in terms of design characteristics, for constructing metamaterials with linear, elliptical, and hyperbolic dispersion relations which produce ENZ behavior, normal or negative diffraction.},
	issn = {2469-9950},
	doi = {10.1103/PhysRevB.94.201404},
	author = {Marios Mattheakis and Constantinos A. Valagiannopoulos and Efthimios Kaxiras}
}
@article { ISI:000381320200006,
	title = {eReaxFF: A Pseudoclassical Treatment of Explicit Electrons within Reactive Force Field Simulations},
	journal = {JOURNAL OF CHEMICAL THEORY AND COMPUTATION},
	volume = {12},
	number = {8},
	year = {2016},
	month = {AUG},
	pages = {3463-3472},
	abstract = {We present a computational tool, eReaxFF, for simulating explicit electrons within the framework of the standard ReaxFF reactive force field method. We treat electrons explicitly in a pseudoclassical manner that enables simulation several orders of magnitude faster than quantum chemistry (QC) methods, while retaining the ReaxFF transferability. We delineate here the fundamental concepts of the eReaxFF method and the integration of the Atom condensed Kohn-Sham DFT approximated to second order (ACKS2) charge calculation scheme into the eReaxFF. We trained our force field to capture electron affinities (EA) of various species. As a proof-of-principle, we performed a set of molecular dynamics (MD) simulations with an explicit electron model for representative hydrocarbon radicals. We establish a good qualitative agreement of EAs of various species with experimental data, and MD simulations with eReaxFF agree well with the corresponding Ehrenfest dynamics simulations. The standard ReaxFF parameters available in the literature are transferrable to the eReaxFF method. The computationally economic eReaxFF method will be a useful tool for studying large-scale chemical and physical systems with explicit electrons as an alternative to computationally demanding QC methods.},
	issn = {1549-9618},
	doi = {10.1021/acs.jctc.6b00432},
	author = {Islam, Md Mahbubul and Grigory Kolesov and Verstraelen, Toon and Efthimios Kaxiras and van Duin, Adri C. T.}
}
@article { ISI:000387309300001,
	title = {Establishing the limits of efficiency of perovskite solar cells from first principles modeling},
	journal = {SCIENTIFIC REPORTS},
	volume = {6},
	year = {2016},
	month = {NOV 8},
	abstract = {The recent surge in research on metal-halide-perovskite solar cells has led to a seven-fold increase of efficiency, from similar to 3\% in early devices to over 22\% in research prototypes. Oft-cited reasons for this increase are: (i) a carrier diffusion length reaching hundreds of microns; (ii) a low exciton binding energy; and (iii) a high optical absorption coefficient. These hybrid organic-inorganic materials span a large chemical space with the perovskite structure. Here, using first-principles calculations and thermodynamic modelling, we establish that, given the range of band-gaps of the metal-halide-perovskites, the theoretical maximum efficiency limit is in the range of similar to 25-27\%. Our conclusions are based on the effect of level alignment between the perovskite absorber layer and carrier-transporting materials on the performance of the solar cell as a whole. Our results provide a useful framework for experimental searches toward more efficient devices.},
	issn = {2045-2322},
	doi = {10.1038/srep36108},
	author = {Granas, Oscar and Dmitry Vinichenko and Efthimios Kaxiras}
}
@article { ISI:000373936300025,
	title = {Excitation intensity dependence of photoluminescence from monolayers of MoS2 and WS2/MoS2 heterostructures},
	journal = {2D MATERIALS},
	volume = {3},
	number = {1},
	year = {2016},
	month = {MAR},
	abstract = {A detailed study of the excitation dependence of the photoluminescence (PL) from monolayers of MoS2 and WS2/MoS2 heterostructures grown by chemical vapor deposition on Si substrates has revealed that the luminescence from band edge excitons from MoS2 monolayers shows a linear dependence on excitation intensity for both above band gap and resonant excitation conditions. In particular, a band separated by similar to 55 meV from the A exciton, referred to as the C band, shows the same linear dependence on excitation intensity as the band edge excitons. A band similar to the C band has been previously ascribed to a trion, a charged, three-particle exciton. However, in our study the C band does not show the 3/2 power dependence on excitation intensity as would be expected for a three-particle exciton. Further, the PL from the MoS2 monolayer in a bilayer WS2/MoS2 heterostructure, under resonant excitation conditions where only the MoS2 absorbs the laser energy, also revealed a linear dependence on excitation intensity for the C band, confirming that its origin is not due to a trion but instead a bound exciton, presumably of an unintentional impurity or a native point defect such as a sulfur vacancy. The PL from the WS2/MoS2 heterostructure, under resonant excitation conditions also showed additional features which are suggested to arise from the interface states at the heteroboundary. Further studies are required to clearly identify the origin of these features.},
	issn = {2053-1583},
	doi = {10.1088/2053-1583/3/1/015005},
	author = {Kaplan, D. and Gong, Y. and Mills, K. and Swaminathan, V. and Ajayan, P. M. and Shirodkar, S. and E. Kaxiras}
}
@article { ISI:000381470200012,
	title = {High-Temperature Quantum Anomalous Hall Effect in n-p Codoped Topological Insulators},
	journal = {PHYSICAL REVIEW LETTERS},
	volume = {117},
	number = {5},
	year = {2016},
	month = {JUL 27},
	abstract = {The quantum anomalous Hall effect (QAHE) is a fundamental quantum transport phenomenon that manifests as a quantized transverse conductance in response to a longitudinally applied electric field in the absence of an external magnetic field, and it promises to have immense application potential in future dissipationless quantum electronics. Here, we present a novel kinetic pathway to realize the QAHE at high temperatures by n-p codoping of three-dimensional topological insulators. We provide a proof-of-principle numerical demonstration of this approach using vanadium-iodine (V-I) codoped Sb2Te3 and demonstrate that, strikingly, even at low concentrations of similar to 2\% V and similar to 1\% I, the system exhibits a quantized Hall conductance, the telltale hallmark of QAHE, at temperatures of at least similar to 50 K, which is 3 orders of magnitude higher than the typical temperatures at which it has been realized to date. The underlying physical factor enabling this dramatic improvement is tied to the largely preserved intrinsic band gap of the host system upon compensated n-p codoping. The proposed approach is conceptually general and may shed new light in experimental realization of high-temperature QAHE.},
	issn = {0031-9007},
	doi = {10.1103/PhysRevLett.117.056804},
	author = {Qi, Shifei and Qiao, Zhenhua and Deng, Xinzhou and Ekin D. Cubuk and Chen, Hua and Wenguang Zhu and Efthimios Kaxiras and Zhang, S. B. and Xu, Xiaohong and Zhenyu Zhang}
}
@article { ISI:000381236100040,
	title = {How Does Nanoporous Gold Dissociate Molecular Oxygen?},
	journal = {JOURNAL OF PHYSICAL CHEMISTRY C},
	volume = {120},
	number = {30},
	year = {2016},
	month = {AUG 4},
	pages = {16636-16640},
	abstract = {Nanoporous Au and other dilute AgAu alloys are highly active and selective oxidation catalysts. Their ability to dissociate O-2 is to a large extent unexplained, given that unsupported Au cannot generally dissociate O-2 while large ensembles of Ag atoms (>4) are generally necessary to lower the O-2 dissociation barrier significantly. Here, we identify a site on the surface of dilute AgAu alloys that is stable under reaction conditions and has a low O-2 dissociation barrier, in agreement with experimental measurements. Although Ag generally prefers to disperse throughout Au, the presence of adsorbed O near surface steps creates sites of high local Ag concentration, where the Ag, atoms sit in the rows next to the step Au atoms. O-2 adsorbs on the Au step atoms, but the transition state involves significant Ag-O interaction, resulting in a barrier lower than expected from the adsorption energies of either the initial or final state.},
	issn = {1932-7447},
	doi = {10.1021/acs.jpcc.6b03371},
	author = {Montemore, Matthew M. and Madix, Robert J. and Efthimios Kaxiras}
}
@article { ISI:000378817100002,
	title = {Li intercalation at graphene/hexagonal boron nitride interfaces},
	journal = {PHYSICAL REVIEW B},
	volume = {93},
	number = {24},
	year = {2016},
	month = {JUN 30},
	abstract = {Intercalation of Li in graphite and other layered structures is of interest for highly efficient energy storage devices. In this paper, we determine the extent to which Li intercalates at the different interfaces formed between graphene (G) and hexagonal boron nitride (hBN) heterostructures. We use ab initio calculations to explore in detail the position of the dispersed Li atoms, changes in the structure at the interfaces, energetic stability of the configurations, and the corresponding electronic structure with varying concentrations of the intercalant. We trace the origin of the energetic stability and maximum concentration of Li that intercalates into various layered structures to the ability of the interface to accept electrons. Our calculations indicate that Li intercalates easiest at G/G interfaces, followed by interfaces between G/hBN, whereas Li cannot intercalate in hBN/hBN interfaces. Our results provide a framework for the design of experimental setups with optimal Li intercalation and reveal the implications of intercalation on the dielectric properties of these materials and their possible application in plasmonics.},
	issn = {2469-9950},
	doi = {10.1103/PhysRevB.93.245438},
	author = {Shirodkar, Sharmila N. and Efthimios Kaxiras}
}
@article { ISI:000368322500003,
	title = {Long-Time Dynamics through Parallel Trajectory Splicing},
	journal = {JOURNAL OF CHEMICAL THEORY AND COMPUTATION},
	volume = {12},
	number = {1},
	year = {2016},
	month = {JAN},
	pages = {18-28},
	abstract = {Simulating the atomistic evolution of materials over long time scales is a longstanding challenge, especially for complex systems where the distribution of barrier heights is very heterogeneous. Such systems are difficult to investigate using conventional long-time scale techniques, and the fact that they tend to remain trapped in small regions of configuration space for extended periods of time strongly limits the physical insights gained from short simulations. We introduce a novel simulation technique, Parallel Trajectory Splicing (Par Splice), that aims at addressing this problem through the timewise parallelization of long trajectories. The computational efficiency of Par Splice stems from a speculation strategy whereby predictions of the future evolution of the system are leveraged to increase the amount of work that can be concurrently performed at any one time, hence improving the scalability of the method. ParSplice is also able to accurately account for, and potentially reuse, a substantial fraction of the computational work invested in the simulation. We validate the method on a simple Ag surface system and demonstrate substantial increases in efficiency compared to previous methods. We then demonstrate the power of ParSplice through the study of topology changes in Ag42Cu13 core shell nanoparticles.},
	issn = {1549-9618},
	doi = {10.1021/acs.jctc.5b00916},
	author = {Perez, Danny and Ekin D. Cubuk and Amos Waterland and Efthimios Kaxiras and Voter, Arthur F.}
}
@article { ISI:000379499900011,
	title = {Mapping reactive flow patterns in monolithic nanoporous catalysts},
	journal = {MICROFLUIDICS AND NANOFLUIDICS},
	volume = {20},
	number = {7},
	year = {2016},
	month = {JUL},
	abstract = {The development of high-efficiency porous catalyst membranes critically depends on our understanding of where the majority of the chemical conversions occur within the porous structure. This requires mapping of chemical reactions and mass transport inside the complex nanoscale architecture of porous catalyst membranes which is a multiscale problem in both the temporal and spatial domains. To address this problem, we developed a multiscale mass transport computational framework based on the lattice Boltzmann method that allows us to account for catalytic reactions at the gas-solid interface by introducing a new boundary condition. In good agreement with experiments, the simulations reveal that most catalytic reactions occur near the gas-flow facing side of the catalyst membrane if chemical reactions are fast compared to mass transport within the porous catalyst membrane.},
	issn = {1613-4982},
	doi = {10.1007/s10404-016-1767-5},
	author = {Falcucci, Giacomo and Sauro Succi and Montessori, Andrea and Simone Melchionna and Prestininzi, Pietro and Barroo, Cedric and Bell, David C. and Biener, Monika M. and Biener, Juergen and Zugic, Branko and Efthimios Kaxiras}
}
@article { ISI:000389963200072,
	title = {MoS2 Field-Effect Transistor with Sub-10 nm Channel Length},
	journal = {NANO LETTERS},
	volume = {16},
	number = {12},
	year = {2016},
	month = {DEC},
	pages = {7798-7806},
	abstract = {Atomically thin molybdenum disulfide (MoS2) is an ideal semiconductor material for field-effect transistors (FETs) with sub-10 nm channel lengths. The high effective mass and large bandgap of MoS2 minimize direct source-drain tunneling, while its atomically thin body maximizes the gate modulation efficiency in ultrashort-channel transistors. However, no experimental study to date has approached the sub-10 nm scale due to the multiple challenges related to nanofabrication at this length scale and the high contact resistance traditionally observed in MoS2 transistors. Here, using the semiconducting-to-metallic phase transition of MoS2, we demonstrate sub-10 nm channel-length transistor fabrication by directed self-assembly patterning of mono- and trilayer MoS2. This is done in a 7.5 nm half-pitch periodic chain of transistors where semiconducting (2H) MoS2 channel regions are seamlessly connected to metallic-phase (1T{\textquoteright}) MoS2 access and contact regions. The resulting 7.5 nm channel-length MoS2 FET has a low off-current of 10 pA/mu m, an on/off current ratio of >10(7), and a subthreshold swing of 120 mV/dec. The experimental results presented in this work, combined with device transport modeling, reveal the remarkable potential of 2D MoS2 for future sub-10 nm technology nodes.},
	issn = {1530-6984},
	doi = {10.1021/acs.nanolett.6b03999},
	author = {Amirhasan Nourbakhsh and Ahmad Zubair and Redwan N. Sajjad and Tavakkoli, Amir K. G. and Chen, Wei and Fang, Shiang and Xi Ling and Jing Kong and Dresselhaus, Mildred S. and Efthimios Kaxiras and Berggren, Karl K. and Dimitri Antoniadis and Tomas Palacios}
}
@article { ISI:000431460204129,
	title = {Non-adiabatic effects and electronic excitations during dissociation on catalytic surfaces},
	journal = {ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY},
	volume = {252},
	year = {2016},
	month = {AUG 20},
	issn = {0065-7727},
	author = {Montemore, Matthew and Robert Hoyt and Efthimios Kaxiras}
}
@article { ISI:000431905700282,
	title = {Non-adiabatic energy dissipation in dissociation on catalytic surface},
	journal = {ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY},
	volume = {251},
	year = {2016},
	month = {MAR 13},
	issn = {0065-7727},
	author = {Montemore, Matthew and Robert Hoyt and Efthimios Kaxiras}
}
@article { ISI:000388913600024,
	title = {Noncovalent Bonding Controls Selectivity in Heterogeneous Catalysis: Coupling Reactions on Gold},
	journal = {JOURNAL OF THE AMERICAN CHEMICAL SOCIETY},
	volume = {138},
	number = {46},
	year = {2016},
	month = {NOV 23},
	pages = {15243-15250},
	abstract = {Enhancing the selectivity of catalytic processes has potential for substantially increasing the sustainability of chemical production. Herein, we establish relationships between reaction selectivity and molecular structure for a homologous series of key intermediates for oxidative coupling of alcohols on gold using a combination of experiment and theory. We establish a scale of binding for molecules with different alkyl structures and chain lengths and thereby demonstrate the critical nature of noncovalent van der Waals interactions in determining the selectivity by modulating the stability of key reaction intermediates bound to the surface. The binding hierarchy is the same for Au(111) and Au(110), which demonstrates a relative lack of sensitivity to the surface structure. The hierarchy of binding established in this work provides guiding principles for predicting how molecular structure affects the competition for binding sites more broadly. Besides the nature of the primary surface-molecule bonding, three additional factors that affect the stabilities of the reactive intermediates are clearly established: (1) the number of C atoms in the alkyl chain, (2) the presence of C-C bond unsaturation, and (3) the degree of branching of the alkyl group of the adsorbed molecules. We suggest that this is a fundamental principle that is generally applicable to a broad range of reactions on metal catalysts.},
	issn = {0002-7863},
	doi = {10.1021/jacs.6b09450},
	author = {Stavros Karakalos and Yunfei Xu and Kabeer, Fairoja Cheenicode and Chen, Wei and Rodriguez-Reyes, Juan Carlos F. and Alexandre Tkatchenko and Efthimios Kaxiras and Madix, Robert J. and Cynthia M. Friend}
}
@article { ISI:000376178400014,
	title = {Perturbation theory for weakly coupled two-dimensional layers},
	journal = {JOURNAL OF MATERIALS RESEARCH},
	volume = {31},
	number = {7},
	year = {2016},
	month = {APR 14},
	pages = {959-966},
	abstract = {A key issue in two-dimensional structures composed of atom-thick sheets of electronic materials is the dependence of the properties of the combined system on the features of its parts. Here, we introduce a simple framework for the study of the electronic structure of layered assemblies based on perturbation theory. Within this framework, we calculate the band structure of commensurate and twisted bilayers of graphene (Gr) and hexagonal boron nitride (h-BN), and of a Gr/h-BN heterostructure, which we compare with reference full-scale density functional theory calculations. This study presents a general methodology for computationally efficient calculations of two-dimensional materials and also demonstrates that for relatively large twist in the graphene bilayer, the perturbation of electronic states near the Fermi level is negligible.},
	issn = {0884-2914},
	doi = {10.1557/jmr.2016.99},
	author = {Tritsaris, Georgios A. and Shirodkar, Sharmila N. and Efthimios Kaxiras and Cazeaux, Paul and Luskin, Mitchell and Plechac, Petr and Cances, Eric}
}
@article { ISI:000370112900002,
	title = {Real-Time TD-DFT with Classical Ion Dynamics: Methodology and Applications},
	journal = {JOURNAL OF CHEMICAL THEORY AND COMPUTATION},
	volume = {12},
	number = {2},
	year = {2016},
	month = {FEB},
	pages = {466-476},
	abstract = {We present a method for real-time propagation of electronic wave functions, within time-dependent density functional theory (RT-TDDFT), coupled to ionic motion through mean-field classical dynamics. The goal of our method is to treat large systems and complex processes, in particular photocatalytic reactions and electron transfer events on surfaces and thin films. Due to the complexity of these processes, computational approaches are needed to provide insight into the underlying physical mechanisms and are therefore crucial for the rational design of new materials. Because of the short time step required for electron propagation (of order similar to 10 attoseconds), these simulations are computationally very demanding. Our methodology is based on numerical atomic-orbital-basis sets for computational efficiency. In the computational package, to which we refer as TDAP-2.0 (Time-evolving Deterministic Atom Propagator), we have implemented a number of important features and analysis tools for more accurate and efficient treatment of large, complex systems and time scales that reach into a fraction of a picosecond. We showcase the capabilities of our method using four different examples: (i) photodissociation into radicals of opposite spin, (ii) hydrogen adsorption on aluminum surfaces, (iii) optical absorption of spin-polarized organic molecule containing a metal ion, and (iv) electron transfer in a prototypical dye sensitized solar cell.},
	issn = {1549-9618},
	doi = {10.1021/acs.jctc.5b00969},
	author = {Grigory Kolesov and Granas, Oscar and Robert Hoyt and Dmitry Vinichenko and Efthimios Kaxiras}
}
@article { ISI:000385539200001,
	title = {Self-assembly of acetate adsorbates drives atomic rearrangement on the Au(110) surface},
	journal = {NATURE COMMUNICATIONS},
	volume = {7},
	year = {2016},
	month = {OCT 12},
	abstract = {Weak inter-adsorbate interactions are shown to play a crucial role in determining surface structure, with major implications for its catalytic reactivity. This is exemplified here in the case of acetate bound to Au(110), where the small extra energy of the van der Waals interactions among the surface-bound groups drives massive restructuring of the underlying Au. Acetate is a key intermediate in electro-oxidation of CO2 and a poison in partial oxidation reactions. Metal atom migration originates at surface defects and is likely facilitated by weakened Au-Au interactions due to bonding with the acetate. Even though the acetate is a relatively small molecule, weak intermolecular interaction provides the energy required for molecular self-assembly and reorganization of the metal surface.},
	issn = {2041-1723},
	doi = {10.1038/ncomms13139},
	author = {Fanny Hiebel and Bonggeun Shong and Chen, Wei and Madix, Robert J. and Efthimios Kaxiras and Cynthia M. Friend}
}
@article { ISI:000390031400009,
	title = {Strain dependence of band gaps and exciton energies in pure and mixed transition-metal dichalcogenides},
	journal = {PHYSICAL REVIEW B},
	volume = {94},
	number = {15},
	year = {2016},
	month = {OCT 27},
	abstract = {{{The ability to fabricate 2D device architectures with desired properties, based on stacking of weakly (van der Waals) interacting atomically thin layers, is quickly becoming reality. In order to design ever more complex devices of this type, it is crucial to know the precise strain and composition dependence of the layers{\textquoteright} electronic and optical properties. Here, we present a theoretical study of these dependences for monolayers with compositions varying from pure MX2 to the mixed MXY, where M = Mo, W and X},
	issn = {2469-9950},
	doi = {10.1103/PhysRevB.94.155310},
	author = {Defo, Rodrick Kuate and Fang, Shiang and Shirodkar, Sharmila N. and Tritsaris, Georgios A. and Dimoulas, Athanasios and Efthimios Kaxiras}
}
@article { ISI:000375255000018,
	title = {A structural approach to relaxation in glassy liquids},
	journal = {NATURE PHYSICS},
	volume = {12},
	number = {5},
	year = {2016},
	month = {MAY},
	pages = {469+},
	abstract = {In contrast with crystallization, there is no noticeable structural change at the glass transition. Characteristic features of glassy dynamics that appear below an onset temperature, T-0 (refs 1-3), are qualitatively captured by mean field theory(4-6), which assumes uniform local structure. Studies of more realistic systems have found only weak correlations between structure and dynamics(7-11). This raises the question: is structure important to glassy dynamics in three dimensions? We answer this question affirmatively, using machine learning to identify a new field, {\textquoteleft}softness{\textquoteright} which characterizes local structure and is strongly correlated with dynamics. We find that the onset of glassy dynamics at T-0 corresponds to the onset of correlations between softness (that is, structure) and dynamics. Moreover, we construct a simple model of relaxation that agrees well with our simulation results, showing that a theory of the evolution of softness in time would constitute a theory of glassy dynamics.},
	issn = {1745-2473},
	doi = {10.1038/NPHYS3644},
	author = {S. S. Schoenholz, and Cubuk, E. D. and Sussman, D. M. and E. Kaxiras and Liu, A. J.}
}
@article { ISI:000379457200040,
	title = {Structural Properties of Defects in Glassy Liquids},
	journal = {JOURNAL OF PHYSICAL CHEMISTRY B},
	volume = {120},
	number = {26},
	year = {2016},
	month = {JUL 7},
	pages = {6139-6146},
	abstract = {At zero temperature a disordered solid corresponds to a local minimum in the energy landscape. As the temperature is raised or the system is driven with a mechanical load, the system explores different minima via dynamical events in which particles rearrange their relative positions. We have shown recently that the dynamics of particle rearrangements are strongly correlated with a structural quantity associated with each particle, {\textquoteleft}{\textquoteleft}softness{\textquoteright}{\textquoteright}, which we can identify using supervised machine learning. Particles of a given softness have a well-defined energy scale that governs local rearrangements; because of this property, softness greatly simplifies our understanding of glassy dynamics. Here we investigate the correlation of softness with other commonly used structural quantities, such as coordination number and local potential energy. We show that although softness strongly correlates with these properties, its predictive power for rearrangement dynamics is much higher. We introduce a useful metric for quantifying the quality of structural quantities as predictors of dynamics. We hope that, in the future, authors introducing new structural measures of dynamics will compare their proposals quantitatively to softness using this metric. We also show how softness correlations give insight into rearrangements. Finally, we explore the physical meaning of softness using unsupervised dimensionality reduction and reduced curve-fitting, models, and show that softness can be recast in a form that is amenable to analytical treatment.},
	issn = {1520-6106},
	doi = {10.1021/acs.jpcb.6b02144},
	author = {Ekin D. Cubuk and Schoenholz, Samuel S. and Efthimios Kaxiras and Liu, Andrea J.}
}
@article { ISI:000431903805422,
	title = {Structure and reactivity of AgAu Alloys},
	journal = {ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY},
	volume = {251},
	year = {2016},
	month = {MAR 13},
	issn = {0065-7727},
	author = {Montemore, Matthew and Efthimios Kaxiras}
}
@article { ISI:000383247500015,
	title = {Superlattice-Induced Insulating States and Valley-Protected Orbits in Twisted Bilayer Graphene},
	journal = {PHYSICAL REVIEW LETTERS},
	volume = {117},
	number = {11},
	year = {2016},
	month = {SEP 7},
	abstract = {Twisted bilayer graphene (TBLG) is one of the simplest van der Waals heterostructures, yet it yields a complex electronic system with intricate interplay between moire physics and interlayer hybridization effects. We report on electronic transport measurements of high mobility small angle TBLG devices showing clear evidence for insulating states at the superlattice band edges, with thermal activation gaps several times larger than theoretically predicted. Moreover, Shubnikov-de Haas oscillations and tight binding calculations reveal that the band structure consists of two intersecting Fermi contours whose crossing points are effectively unhybridized. We attribute this to exponentially suppressed interlayer hopping amplitudes for momentum transfers larger than the moire wave vector.},
	issn = {0031-9007},
	doi = {10.1103/PhysRevLett.117.116804},
	author = {Cao, Y. and Luo, J. Y. and Fatemi, V. and Fang, S. and Sanchez-Yamagishi, J. D. and K. Watanabe and T. Taniguchi and E. Kaxiras and P. Jarillo-Herrero}
}
@article { ISI:000370987400125,
	title = {Theory of Graphene Raman Scattering},
	journal = {ACS NANO},
	volume = {10},
	number = {2},
	year = {2016},
	month = {FEB},
	pages = {2803-2818},
	abstract = {Raman scattering plays a key role in unraveling the quantum dynamics of graphene, perhaps the most promising material of recent times. It is crucial to correctly interpret the meaning of the spectra. It is therefore very surprising that the widely accepted understanding of Raman scattering, i.e., Kramers Heisenberg Dirac theory, has never been applied to graphene. Doing so here, a remarkable mechanism we term{\textquoteright}{\textquoteright}transition sliding{\textquoteright}{\textquoteright} is uncovered, explaining the uncommon brightness of overtones in graphene. Graphene{\textquoteright}s dispersive and fixed Raman bands, missing bands, defect density and laser frequency dependence of band intensities, widths of overtone bands, Stokes, anti -Stokes anomalies, and other known properties emerge simply and directly.},
	issn = {1936-0851},
	doi = {10.1021/acsnano.5b07676},
	author = {Heller, Eric J. and Yang, Yuan and Kocia, Lucas and Chen, Wei and Fang, Shiang and Borunda, Mario and Efthimios Kaxiras}
}
@article { ISI:000364159900002,
	title = {Ab initio tight-binding Hamiltonian for transition metal dichalcogenides},
	journal = {PHYSICAL REVIEW B},
	volume = {92},
	number = {20},
	year = {2015},
	month = {NOV 5},
	abstract = {We present an accurate ab initio tight-binding Hamiltonian for the transition metal dichalcogenides, MoS2, MoSe2, WS2, WSe2, with a minimal basis (the d orbitals for the metal atoms and p orbitals for the chalcogen atoms) based on a transformation of theKohn-Sham density functional theory Hamiltonian to a basis of maximally localized Wannier functions. The truncated tight-binding Hamiltonian, with only on-site, first, and partial second neighbor interactions, including spin-orbit coupling, provides a simple physical picture and the symmetry of the main band-structure features. Interlayer interactions between adjacent layers are modeled by transferable hopping terms between the chalcogen p orbitals. The full-range tight-binding Hamiltonian can be reduced to hybrid-orbital k . p effective Hamiltonians near the band extrema that capture important low-energy excitations. These ab initio Hamiltonians can serve as the starting point for applications to interacting many-body physics including optical transitions and Berry curvature of bands, of which we give some examples.},
	issn = {1098-0121},
	doi = {10.1103/PhysRevB.92.205108},
	author = {Fang, Shiang and Defo, Rodrick Kuate and Shirodkar, Sharmila N. and Lieu, Simon and Tritsaris, Georgios A. and Efthimios Kaxiras}
}
@article { ISI:000355014900023,
	title = {Anatomy of the Photochemical Reaction: Excited-State Dynamics Reveals the C-H Acidity Mechanism of Methoxy Photo-oxidation on Titania},
	journal = {JOURNAL OF PHYSICAL CHEMISTRY LETTERS},
	volume = {6},
	number = {9},
	year = {2015},
	month = {MAY 7},
	pages = {1624-1627},
	abstract = {Light-driven chemical reactions on semiconductor surfaces have potential for addressing energy and pollution needs through efficient chemical synthesis; however, little is known about the time evolution of excited states that determine reaction pathways. Here, we study the photo-oxidation of methoxy (CH3O) derived from methanol on the rutile TiO2(110) surface using ab initio simulations to create a molecular movie of the process. The movie sequence reveals a wealth of information on the reaction intermediates, time scales, and energetics. The reaction is broken in three stages, described by Lewis structures directly derived from the {\textquoteleft}{\textquoteleft}hole{\textquoteright}{\textquoteright} wave functions that lead to the concept of {\textquoteleft}{\textquoteleft}photoinduced C-H acidity{\textquoteright}{\textquoteright}. The insights gained from this work can be generalized to a set of simple rules that can predict the efficiency of photo-oxidation reactions in reactant-catalyst pairs.},
	issn = {1948-7185},
	doi = {10.1021/acs.jpclett.5b00429},
	author = {Grigory Kolesov and Dmitry Vinichenko and Tritsaris, Georgios A. and Cynthia M. Friend and Efthimios Kaxiras}
}
@article { ISI:000357263300016,
	title = {Revealing the Empty-State Electronic Structure of Single-Unit-Cell FeSe/SrTiO3},
	journal = {PHYSICAL REVIEW LETTERS},
	volume = {115},
	number = {1},
	year = {2015},
	month = {JUL 2},
	abstract = {We use scanning tunneling spectroscopy to investigate the filled and empty electronic states of superconducting single-unit-cell FeSe deposited on SrTiO3(001). We map the momentum-space band structure by combining quasiparticle interference imaging with decay length spectroscopy. In addition to quantifying the filled-state bands, we discover a Gamma-centered electron pocket 75 meV above the Fermi energy. Our density functional theory calculations show the orbital nature of empty states at Gamma and explain how the Se height is a key tuning parameter of their energies, with broad implications for electronic properties.},
	issn = {0031-9007},
	doi = {10.1103/PhysRevLett.115.017002},
	author = {Huang, Dennis and Song, Can-Li and Webb, Tatiana A. and Fang, Shiang and Chang, Cui-Zu and Moodera, Jagadeesh S. and Efthimios Kaxiras and Hoffman, Jennifer E.}
}
@article {277366,
	title = {Revealing the Empty-State Electronic Structure of Single-Unit-Cell FeSe /SrTiO3},
	journal = {Physical Review Letters},
	volume = {115},
	year = {2015},
	pages = {017002},
	abstract = {We use scanning tunneling spectroscopy to investigate the filled and empty electronic states of superconducting single-unit-cell FeSe deposited on\&nbsp;SrTiO3(001). We map the momentum-space band structure by combining quasiparticle interference imaging with decay length spectroscopy. In addition to quantifying the filled-state bands, we discover a\&nbsp;Γ-centered electron pocket 75\&nbsp;meV above the Fermi energy. Our density functional theory calculations show the orbital nature of empty states at\&nbsp;Γ\&nbsp;and explain how the Se height is a key tuning parameter of their energies, with broad implications for electronic properties.},
	author = {Huang, Dennis and Song, Can-Li and Webb, Tatiana A. and Fang, Shiang and Chang, Cui-Zu and Moodera, Jagadeesh S. and Efthimios Kaxiras and Hoffman, Jennifer E.}
}
@article {271341,
	title = {Stress effects on the initial lithiation of crystalline silicon nanowires: reactive molecular dynamics simulations using ReaxFF},
	journal = {Physical Chemistry Chemical Physics},
	volume = {17},
	year = {2015},
	pages = {3832-3840},
	abstract = {
	Silicon (Si) has been recognized as a promising anode material for the next-generation high-capacity lithium (Li)-ion batteries because of its high theoretical energy density. Recent in situ transmission electron microscopy (TEM) revealed that the electrochemical lithiation of crystalline Si nanowires(c-SiNWs) proceeds by the migration of the interface between the lithiated Si (LixSi) shell and the pristine unlithiated core, accompanied by solid-state amorphization. The underlying atomic mechanisms of Li insertion into c-Si remain poorly understood. Herein, we perform molecular dynamics (MD) simulations using the reactive force field (ReaxFF) to characterize the lithiation process of c-SiNWs. Our calculations show that ReaxFF can accurately reproduce the energy barriers of Li migration from DFT calculations inboth crystalline (c-Si) and amorphous Si (a-Si). The ReaxFF-based MD simulations reveal that Li insertion into interlayer spacing between two adjacent (111) planes results in the peeling-off of the (111) facets and subsequent amorphization, in agreement with experimental observations. We find that breaking of the Si{\textendash}Si bonds between (111)-bilayers requires a rather high local Li concentration, which explains the atomically sharp amorphous{\textendash}crystalline interface (ACI). Our stress analysis shows that lithiation induces compressive stress at the ACI layer, causing retardation or even the stagnation of the reaction front, also in good agreement with TEM observations. Lithiation at high temperatures (e.g. 1200 K) shows that Li insertion into c-SiNW results in an amorphous to crystalline phase transformation at Li : Si compositionof B4.2 : 1. Our modeling results provide a comprehensive picture of the effects of reaction and diffusion-induced stress on the interfacial dynamics and mechanical degradation of SiNW anodes under chemo-mechanical lithiation.

},
	author = {Alireza Ostadhossein and Ekin D. Cubuk and Tritsaris, Georgios A. and Efthimios Kaxiras and Sulin Zhang and van Duin, Adri C. T.}
}
@article {259776,
	title = {Anatomy of the Photochemical Reaction: Excited-State Dynamics Reveals the C-H Acidity Mechanism of Methoxy Photo-oxidation on Titania},
	journal = {Journal of Physical Chemistry Letters},
	volume = {6},
	year = {2015},
	pages = {1624-1627},
	abstract = {Light-driven chemical reactions on semiconductor surfaces have potential foraddressing energy and pollution needs through efficient chemical synthesis; however, little is known about the time evolution of excited states that determine reaction pathways. Here, we study the photo-oxidation of methoxy (CH3O) derived from methanol on the rutile TiO2(110) surface using ab initio simulations to create a molecular movie of the process. The movie sequence reveals a wealth of information on the reaction intermediates, time scales, and energetics. The reaction is broken in three stages, described by Lewis structures directly derived from the {\textquotedblleft}hole{\textquotedblright} wave functions that lead to the concept of {\textquotedblleft}photoinduced C-H acidity{\textquotedblright}. The insights gained from this work can be generalized to a set of simple rules that can predict the efficiency of photo-oxidation reactions in reactant-catalyst pairs.},
	author = {Grigory Kolesov and Dmitry Vinichenko and Georgios A. Tritsaris and Cynthia M. Friend and Efthimios Kaxiras}
}
@article {259781,
	title = {Atomistic mechanisms for bilayer growth of graphene on metal substrates},
	journal = {Physical Review B},
	volume = {91},
	year = {2015},
	pages = {045408},
	abstract = {Epitaxial growth on metal substrates has been shown to be the most powerful approach in producing large-scale high-quality monolayer graphene, yet it remains a major challenge to realize uniform bilayer graphene growth. Here we carry out a comparative study of the atomistic mechanisms for bilayer graphene growth on the (111) surfaces of Cu and Ni, using multiscale approaches combining first-principles calculations and rate-equation analysis. We first show that the relatively weak graphene-Cu interaction enhances the lateral diffusion and effective nucleation of C atoms underneath the graphene island, thereby making it more feasible to grow bilayer graphene on Cu. In contrast, the stronger graphene-Ni interaction suppresses the lateral mobility and dimerization of C atoms underneath the graphene, making it unlikely to achieve controlled growth of bilayer graphene on Ni. We then determine the critical graphene size beyond which nucleation of the second layer will take place. Intriguingly, the critical size exhibits an effective inverse {\textquotedblleft}Ehrlich-Schwoebel barrier{\textquotedblright} effect, becoming smallerfor faster C migration from the Cu surface to the graphene-Cu interface sites across the graphene edge. These findings allow us to propose a novel alternating growth scheme to realize mass production of bilayer graphene.},
	author = {Chen, Wei and Ping Cui and Wenguang Zhu and Efthimios Kaxiras and Yanfei Gao and Zhenyu Zhang}
}
@article {259786,
	title = {Identifying Structural Flow Defects in Disordered Solids Using Machine-Learning Methods},
	journal = {Physical Review Letters},
	volume = {114},
	year = {2015},
	pages = {108001},
	abstract = {We use machine-learning methods on local structure to identify flow defects{\textemdash}or particles susceptible to rearrangement{\textemdash}in jammed and glassy systems. We apply this method successfully to two very different systems: a two-dimensional experimental realization of a granular pillar under compression and a Lennard-Jones glass in both two and three dimensions above and below its glass transition temperature. We also identify characteristics of flow defects that differentiate them from the rest of the sample. Our results show it is possible to discern subtle structural features responsible for heterogeneous dynamics observed across a broad range of disordered materials.},
	author = {E. D. Cubuk and S. S. Schoenholz, and J. M. Rieser and B. D. Malone and J. Rottler and D. J. Durian and E. Kaxiras and A. J. Liu}
}
@article {233461,
	title = {Direct Observation of a Long-Lived Single-Atom Catalyst Chiseling Atomic Structures in Graphene},
	journal = {NanoLetters},
	volume = {14},
	year = {2014},
	pages = {450-455},
	abstract = {Fabricating stable functional devices at the atomic scale is an ultimate goal of nanotechnology. In biological processes, such high-precision operations are accomplished by enzymes. A counterpart molecular catalyst that binds to a solid-state substrate would be highly desirable. Here, we report the direct observation of single Si adatoms catalyzing the dissociation of carbon atoms from graphene in an aberrationcorrected high-resolution transmission electron microscope (HRTEM). The single Si atom provides a catalytic wedge for energetic electrons to chisel off the graphene lattice, atom by atom, while the Si atom itself is not consumed. The products of the chiseling process are atomic-scale features including graphene pores and clean edges. Our experimental observations and first-principles calculations demonstrated the dynamics, stability, and selectivity of such a single-atom chisel, which opens up the possibility of fabricating certain stable molecular devices by precise modification of materials at the atomic scale.},
	author = {Wei Li Wang and Elton J. G. Santos and Bin Jiang and Ekin Dogus Cubuk and Colin Ophus and Alba Centeno and Amaia Pesquera and Amaia Zurutuza and Jim Ciston and Robert Westervelt and Efthimios Kaxiras}
}
@article {233481,
	title = {Dynamics of the Photogenerated Hole at the Rutile TiO2(110)/Water Interface: A Nonadiabatic Simulation Study},
	journal = {Journal of Physical Chemistry C },
	volume = {118},
	year = {2014},
	pages = {27393-27401},
	abstract = {Hydrogen production in photoelectrochemical cells constitutes an important avenue toward carbon-free fuel. The most convenient process for hydrogen production is the splitting of water molecules, which necessitates a catalyticreaction involving a semiconductor. Here, we introduce a framework for the study of photocatalyzed reactions on semiconductor surfaces based on time-dependent density functional theory that explicitly accounts for the evolution of electronically excited states. Within this framework, we investigate the possibility of hole-mediated splitting of molecularly adsorbed water on a representative metal oxide surface the rutile TiO2(110). We find that oxidative dehydrogenation of water is possible in synergy with thermal effects at temperatures between 60 and 100 K only when defects like Ti interstitials are present in the subsurface region. This study presents a general computational strategy for describing photoexcited semiconductor/adsorbate interfaces and also demonstrates that the occurrence of water dissociation on the rutile TiO2(110) surface depends sensitively on the local atomic environment and external parameters such as temperature.},
	author = {Georgios A. Tritsaris and Dmitry Vinichenko and Grigory Kolesov and Cynthia M. Friend and Efthimios Kaxiras}
}
@article {233486,
	title = {First principles study of point defects in SnS},
	journal = {Physical Chemistry Chemical Physics},
	volume = {16},
	year = {2014},
	pages = {26176-26183},
	abstract = {Photovoltaic cells based on SnS as the absorber layer show promise for efficient solar devices containing non-toxic materials that are abundant enough for large scale production. The efficiency of SnS cells has been increasing steadily, but various loss mechanisms in the device, related to the presence of defects in the material, have so far limited it far below its maximal theoretical value. In this work we perform first principles, density-functional-theory calculations to examine the behavior and nature of both intrinsic and extrinsic defects in the SnS absorber layer. We focus on the elements known to exist in the environment of SnS-based photovoltaic devices during growth. In what concerns intrinsic defects, our calculations support the current understanding of the role of the Sn vacancy (VSn) acceptor defect, namely that it is responsible for the p-type conductivity in SnS. We also present calculations for extrinsic defects and make extensive comparison to experimental expectations. Our detailed treatment of electrostatic correction terms for charged defects provides theoretical predictions on both the highfrequency and low-frequency dielectric tensors of SnS.},
	author = {Brad D. Malone and Adam Gali and Efthimios Kaxiras}
}
@article {233466,
	title = {Graphene/MoS2 Hybrid Technology for Large-Scale Two-Dimensional Electronics},
	journal = {NanoLetters},
	volume = {14},
	year = {2014},
	pages = {30553063},
	abstract = {Two-dimensional (2D) materials have generated great interest in the past few years as a new toolbox for electronics. This family of materials includes, among others, metallic graphene, semiconducting transition metal dichalcogenides (such as MoS2), and insulating boron nitride. These materials and their heterostructures offer excellent mechanical flexibility, optical transparency, and favorable transport properties for realizing electronic, sensing, and optical systems on arbitrary surfaces. In this paper, we demonstrate a novel technology for constructing large-scale electronic systems based on graphene/molybdenum disulfide (MoS2) heterostructures grown by chemical vapor deposition. We have fabricated highperformance devices and circuits based on this heterostructure, where MoS2 is used as the transistor channel and graphene as contact electrodes and circuit interconnects. We provide a systematic comparison of the graphene/MoS2 heterojunction contact to more traditional MoS2-metal junctions, as well as a theoretical investigation, using density functional theory, of the origin of the Schottky barrier height. The tunability of the graphene work function with electrostatic doping significantly improves the ohmic contact to MoS2. These high-performance large-scale devices and circuits based on this 2D heterostructure pave the way for practical flexible transparent electronics.},
	author = {Lili Yu and Yi-Hsien Lee and Xi Ling and Elton J. G. Santos and Yong Cheol Shin and Yuxuan Lin and Madan Dubey and Efthimios Kaxiras and Jing Kong and Han Wang and Tomás Palacios}
}
@article {233471,
	title = {Parallel in time approximation of the lattice Boltzmann method for laminar flows},
	journal = {Journal of Computational Physics},
	volume = {270},
	year = {2014},
	pages = {577-586},
	abstract = {Fluid dynamics simulations using grid-based methods, such as the lattice Boltzmann equation, can benefit from parallel-in-space computation. However, for a fixed-size simulation of this type, the efficiency of larger processor counts will saturate when the number of grid points per core becomes too small. To overcome this fundamental strong scaling limit in space-parallel approaches, we present a novel time-parallel version of the lattice Boltzmann method using the parareal algorithm. This method is based on a predictor{\textendash}corrector scheme combined with mesh refinement to enable the simulation of larger number of time steps. We present results of up to a 32{\texttimes} increase in speed for a model system consisting of a cylinder with conditions for laminar flow. The parallel gain obtainable is predicted with strong accuracy, providing a quantitative understanding of the potential impact of this method.},
	author = {Amanda Randles and Efthimios Kaxiras}
}
@article {233476,
	title = {Quantum phase transitions and topological proximity effects in graphene nanoribbon heterostructures},
	journal = {Nanoscale},
	volume = {6},
	year = {2014},
	pages = {3259-3267},
	abstract = {Topological insulators are bulk insulators that possess robust chiral conducting states along their interfaces with normal insulators. A tremendous research effort has recently been devoted to topological insulatorbased heterostructures, in which conventional proximity effects give rise to a series of exotic physical phenomena. Here we establish the potential existence of topological proximity effects at the interface between a topological insulator and a normal insulator, using graphene-based heterostructures as prototypical systems. Unlike conventional proximity effects in topological insulator based heterostructures, which refer to various phase transitions associated with the symmetry breaking of specific local order parameters, topological proximity effects describe the rich variety of quantum phase transitions associated with the global properties of the system measured by the location of the topological edge states. Specifically, we show that the location of the topological edge states exhibits a versatile tunability as a function of the interface orientation, the strength of the interface tunnel coupling between a topological graphene nanoribbon and a normal graphene nanoribbon, the spin{\textendash}orbit coupling strength in the normal graphene nanoribbon, and the width of the system. For zigzag and bearded graphene nanoribbons, the topological edge states can be tuned to be either at the interface or outer edge of the normal ribbon. For armchair graphene nanoribbons, the potential location of the topological edge state can be further shifted to the edge of or within the normal ribbon, to the interface, or diving into the topological graphene nanoribbon. We further show that the topological phase diagram established for the prototypical graphene heterostructures can also explain the intriguing quantum phase transition reported recently in other topological-insulator heterostructures. We also discuss potential experimental realizations of the predicted topological proximity effects, which may pave the way for integrating the salient functionality of topological insulators and graphene in future device applications.},
	author = {Gufeng Zhang and Xiaoguang Li and Guangfen Wu and Jie Wang and Dimitrie Culcer and Efthimios Kaxiras and Zhenyu Zhang}
}
@proceedings {233491,
	title = {A Spatio-Temporal Coupling Method to Reduce the Time-to-Solution of Cardiovascular Simulations},
	journal = {2014 IEEE 28th International Parallel \& Distributed Processing Symposium},
	year = {2014},
	pages = {593-602},
	publisher = {IEEE Computer Society},
	abstract = {We present a new parallel-in-time method designed to reduce the overall time-to- solution of a patientspecific cardiovascular flow simulation. Using a modified parareal algorithm, our approach extends strong scalability beyond spatial parallelism with fully controllable accuracy and no decrease in stability. We discuss the coupling of spatial and temporal domain decompositions used in our implementation, and showcase the use of the method on a study of blood flow through the aorta. We observe an additional 40\% reduction in overall wall clock time with no significant loss of accuracy, in agreement with a predictive performance model.},
	author = {Amanda Randles and Efthimios Kaxiras}
}
@article {233456,
	title = {Surface Plasmon Engineering in Graphene Functionalized with Organic Molecules: A Multiscale Theoretical Investigation},
	journal = {NanoLetters},
	volume = {14},
	year = {2014},
	pages = {50-56},
	abstract = {Graphene was recently shown to support deep subwavelength surface plasmons at terahertz frequencies characterized by low energy loss and strong field localization, both highly desirable. The properties of graphene can be locally tuned by applying an external gate voltage or by the adsorption of organic molecules that lead to doping through charge transfer. Local tuning of the electronic features of graphene opens the possibility to realize any desired gradient index profile and thus brings large flexibility to control and manipulate the propagation of surface plasmons. Here, we explore this possibility created by functionalizing graphene with organic molecules. We employ a multiscale theoretical approach that combines firstprinciples electronic structure calculations and finite-difference time-domain simulations coupled by surface conductivity. We show that by patterning two types of organic molecules on graphene, a plasmonic metasurface can be realized with any gradient effective refractive index profile to manipulate surface plasmon beams as desired. The special properties of such devices based on functionalized graphene are compared to the similar metamaterials based on metallic films on top of a gradient index dielectric substrate. Using this idea, we design and analyze an ultrathin broadband THz plasmonic lens as proof-of-concept, while more sophisticated index profiles can also be realized and various plasmonic applications are readily accessible.},
	author = {Jierong Cheng and Wei Li Wang and Hossein Mosallaei and Efthimios Kaxiras}
}
@article {226826,
	title = {Epitaxial Growth of Molecular Crystals on van der Waals Substrates for High-Performance Organic Electronics},
	journal = {Advanced Materials},
	volume = {26},
	year = {2014},
	pages = {2812-2817},
	author = {Chul-Ho Lee and Theanne Schiros and Elton J. G. Santos and Bumjung Kim and Kevin G. Yager and Seok Ju Kang and Sunwoo Lee and Jaeeun Yu and Kenji Watanabe and Takashi Taniguchi and James Hone and Efthimios Kaxiras and Colin Nuckolls and Philip Kim}
}
@article {226831,
	title = {Qualitative link between work of adhesion and thermal conductance of metal/diamond interfaces},
	journal = {Journal of Applied Physics},
	volume = {115},
	year = {2014},
	pages = {123509},
	abstract = {We report Time-Domain ThermoReflectance experiments measuring the Thermal Boundary Conductance (TBC) of interfaces between diamond and metal surfaces, based on samples consisting of [111]-oriented diamond substrates with hydrogen or with sp2 carbon surface terminations created using plasma treatments. In a concurrent theoretical study, we calculate the work of adhesion between Ni, Cu, and diamond interfaces with (111) surface orientation, with or without hydrogen termination of the diamond surface, using first-principles electronic structure calculations based on density functional theory (DFT). We find a positive correlation between the calculated work of adhesion and the measured conductance of these interfaces, suggesting that DFT could be used as a screening tool to identify metal/dielectric systems with high TBC. We also explain the negative effect of hydrogen on the thermal conductance of metal/diamond interfaces.},
	author = {Christian Monachon and Georg Schusteritsch and Efthimios Kaxiras and Ludger Weber}
}
@article {226836,
	title = {Structural stability and electronic properties of low-index surfaces of SnS},
	journal = {Journal of Applied Physics},
	volume = {115},
	year = {2014},
	pages = {173702},
	abstract = {Thin film photovoltaic cells are increasingly important for cost-effective solar energy harvesting. Layered SnS is a promising absorber material due to its high optical absorption in the visible and good doping characteristics. We use first-principles calculations based on density functional theory to study structures of low-index surfaces of SnS using stoichiometric and oxygen-containing structural models, in order to elucidate their possible effect on the efficiency of the photovoltaic device. We find that the surface energy is minimized for the surface with orientation parallel to the layer stacking direction. Compared to stoichiometric surfaces, the oxygen-containing surfaces exhibit fewer electronic states near the band gap. This reduction of near-gap surface states by oxygen should reduce recombination losses at grain boundaries and interfaces of the SnS absorber, and should be beneficial to the efficiency of the solar cell.},
	author = {Georgios A. Tritsaris and Brad D. Malone and Efthimios Kaxiras}
}
@article {tritsaris2013adsorption,
	title = {Adsorption and diffusion of lithium on layered silicon for Li-ion storage},
	journal = {Nano letters},
	volume = {13},
	number = {5},
	year = {2013},
	pages = {2258{\textendash}2263},
	publisher = {ACS Publications},
	doi = {10.1021/nl400830u},
	author = {Georgios A. Tritsaris and Efthimios Kaxiras and Sheng Meng and Enge Wang}
}
@article {144546,
	title = {Electrically Driven Tuning of the Dielectric Constant in MoS2 Layers},
	journal = {ACS Nano},
	volume = {12},
	year = {2013},
	pages = {10741-10746},
	abstract = {The properties of two-dimensional materials, such as molybdenum disulfide, will play an important role in the design of the next generation of electronic devices. Many of those properties are determined by the dielectric constant which is one of the fundamental quantities used to characterize conductivity, refractive index, charge screening, and capacitance. We predict that the effective dielectric constant (ε) of few-layer MoS2 is tunable by an external electric field (Eext). Through first-principles electronic structure calculations, including van der Waals interactions, we show that at low fields (Eext \&lt; 0.01 V/{\r A}) ε assumes a nearly constant value \~{}4 but increases at higher fields to values that depend on the layer thickness. The thicker the structure, the stronger the modulation of ε with the electric field. Increasing of the external field perpendicular to the dichalcogenide layers beyond a critical value can drive the system to an unstable state where the layers are weakly coupled and can be easily separated. The observed dependence of ε on the external field is due to charge polarization driven by the bias. Implications on the optical properties as well as on the electronic excitations are also considered. Our results point to a promising way of understanding and controlling the screening properties of MoS2 through external electric fields.},
	author = {Elton J. G. Santos and Efthimios Kaxiras}
}
@article {137106,
	title = {Adsorption and Diffusion of Lithium on Layered Silicon for Li-Ion Storage},
	journal = {Nano Letters},
	volume = {13},
	year = {2013},
	pages = {2258-2263},
	abstract = {The energy density of Li-ion batteries depends critically on the specific charge capacity of the constituent electrodes. Silicene, the silicon analogue to graphene, being of atomic thickness could serve as high-capacity host of Li in Li-ion secondary batteries. In this work, we employ first-principles calculations to investigate the interaction of Li with Si in model electrodes of free-standing single-layer and double-layer silicene. More specifically, we identify strong binding sites for Li, calculate the energy barriers accompanying Li diffusion, and present our findings in the context of previous theoretical work related to Liion storage in other structural forms of silicon: the bulk and nanowires. The binding energy of Li is \~{}2.2 eV per Li atom and shows small variation with respect to Li content and silicene thickness (one or two layers) while the barriers for Li diffusion are relatively low, typically less than 0.6 eV. We use our theoretical findings to assess the suitability of two-dimensional silicon in the form of silicene layers for Li-ion storage.},
	author = {Georgios A. Tritsaris and Efthimios Kaxiras and Sheng Meng and Enge Wang}
}
@article {137131,
	title = {Efficient calculation of the effective single-particle potential and its application in electron microscopy},
	journal = {Physical Review B},
	volume = {87},
	year = {2013},
	pages = {085103},
	abstract = {We present an efficient method for obtaining the effective single-particle potential for electrons within density functional theory (DFT). In contrast to the independent atom model (IAM) often used to interpret microscopy experiments, our method includes the contributions from charge redistribution and exchange-correlation interactions in a realistic system. The method allows calculation of the effective potential through the widely used pseudopotential formalism instead of the costly all-electron calculations. A transferable and spin-independent core potential for each element is calculated once and for all. The nonlinear exchange-correlation interaction is treated explicitly. This scheme can be readily implemented in pseudopotential DFT codes. We demonstrate the usefulness of our method by calculating the scattering potential and simulating images of nitrogen point defects in graphene for transmission electron microscopy (TEM). The results are in good agreement with experiments.},
	author = {Wei L. Wang and Efthimios Kaxiras}
}
@article {137116,
	title = {Electric-Field Dependence of the Effective Dielectric Constant in Graphene},
	journal = {Nano Letters},
	volume = {13},
	year = {2013},
	pages = {898-902},
	abstract = {The dielectric constant of a material is one of the fundamental features used to characterize its electrostatic properties such as capacitance, charge screening, and energy storage capability. Graphene is a material with unique behavior due to its gapless electronic structure and linear dispersion near the Fermi level, which can lead to a tunable band gap in bilayer and trilayer graphene, a superconducting-insulating transition in hybrid systems driven by electric fields, and gatecontrolled surface plasmons. All of these results suggest a strong interplay between graphene properties and external electric fields. Here we address the issue of the effective dielectric constant (ε) in N-layer graphene subjected to out-ofplane (Eext ⊥ ) and in-plane (Eext || ) external electric fields. The value of ε has attracted interest due to contradictory reports from theoretical and experimental studies. Through extensive first-principles electronic structure calculations, including van der Waals interactions, we show that both the out-of-plane (ε⊥) and the in-plane (ε||) dielectric constants depend on the value of applied field. For example, ε⊥ and ε|| are nearly constant (\~{}3 and \~{}1.8, respectively) at low fields (Eext \&lt; 0.01 V/{\r A}) but increase at higher fields to values that are dependent on the system size. The increase of the external field perpendicular to the graphene layers beyond a critical value can drive the system to a unstable state where the graphene layers are decoupled and can be easily separated. The observed dependence of ε⊥ and ε|| on the external field is due to charge polarization driven by the bias. Our results point to a promising way of understanding and controlling the screening properties of few-layer graphene through external electric fields.},
	author = {Elton J. G. Santos and Efthimios Kaxiras}
}
@article {137111,
	title = {Morphological Evolution of Si Nanowires upon Lithiation: A First- Principles Multiscale Model},
	journal = {Nano Letters},
	volume = {13},
	year = {2013},
	pages = {2011-2015},
	abstract = {Silicon is a promising anode material for high-capacity Li-ion batteries. Recent experiments show that lithiation of crystalline silicon nanowires leads to highly anisotropic morphologies. This has been interpreted as due to anisotropy in equilibrium interface energies, but this interpretation does not capture the dynamic, nonequilibrium nature of the lithiation process. Here, we provide a comprehensive explanation of experimentally observed morphological changes, based on first-principles multiscale simulations. We identify reaction paths and associated structural transformations for Li insertion into the Si {110} and {111} surfaces and calculate the relevant energy barriers from density functional theory methods. We then perform kinetic Monte Carlo simulations for nanowires with surfaces of different orientations, which reproduce to a remarkable degree the experimentally observed profiles and the relative reaction front rates},
	author = {Ekin D. Cubuk and Wei L. Wang and Kejie Zhao and Joost J. Vlassak and Zhigang Suo and Efthimios Kaxiras}
}
@article {137126,
	title = {Optoelectronic properties of single-layer, double-layer, and bulk tin sulfide: A theoretical study},
	journal = {Journal of Applied Physics},
	volume = {113},
	year = {2013},
	pages = {233507},
	abstract = {SnS\&nbsp;is a metal monochalcogenide suitable for use as absorber\&nbsp;material\&nbsp;in thin film\&nbsp;photovoltaic cells.\&nbsp;Its\&nbsp;structure\&nbsp;is an orthorhombic crystal of weakly coupled layers, each layer consisting of strongly bonded Sn-S units. We use first-principles calculations to study model single-layer, double-layer, and bulk\&nbsp;structures\&nbsp;of\&nbsp;SnS\&nbsp;in order to elucidate its electronic structure. We find that the optoelectronic\&nbsp;properties\&nbsp;of the\&nbsp;material\&nbsp;can vary significantly with respect to the number of layers and the separation between them: the calculated\&nbsp;band gap\&nbsp;is wider for fewer layers (2.72 eV, 1.57 eV, and 1.07 eV for single-layer, double-layer, and bulk\&nbsp;SnS,\&nbsp;respectively) and increases with tensile strain along the layer stacking direction (by \~{}55 meV/1\% strain).},
	author = {Georgios A. Tritsaris and Brad D. Malone and Efthimios Kaxiras}
}
@article {137136,
	title = {Quasiparticle band structures and interface physics of SnS and GeS},
	journal = {Physical Review B},
	volume = {87},
	year = {2013},
	pages = {245312},
	abstract = {We perform first-principles, density-functional-theory calculations of the electronic structure for the layered bulk materials SnS and GeS which are of interest for photovoltaic applications. Band gap corrections are computed within the GW approximation to the electron self-energy. The resulting quasiparticle gaps in both SnS and GeS are in excellent agreement with the majority of existing experimental measurements. In order to better understand the possible use of GeS layers as a carrier-confining barrier within a SnS-based photovoltaic device, we compute the band offsets for different orientations of a SnS/GeS heterojunction. We find the valence band offsets to be almost independent of interfacial direction while the conduction band offsets show a strong anisotropy as a result of the variation in the band gap caused by epitaxial strain along the different directions.},
	author = {Brad D. Malone and Efthimios Kaxiras}
}
@article {137121,
	title = {Tuning the Electronic and Chemical Properties of Monolayer MoS2 Adsorbed on Transition Metal Substrates},
	journal = {Nano Letters},
	volume = {13},
	year = {2013},
	pages = {509-514},
	abstract = {Using first-principles calculations within density functional theory, we investigate the electronic and chemical properties of a single-layer MoS2 adsorbed on Ir(111), Pd(111), or Ru(0001), three representative transition metal substrates having varying work functions but each with minimal lattice mismatch with the MoS2 overlayer. We find that, for each of the metal substrates, the contact nature is of Schottky-barrier type, and the dependence of the barrier height on the work function exhibits a partial Fermi-level pinning picture. Using hydrogen adsorption as a testing example, we further demonstrate that the introduction of a metal substrate can substantially alter the chemical reactivity of the adsorbed MoS2 layer. The enhanced binding of hydrogen, by as much as \~{}0.4 eV, is attributed in part to a stronger H-S coupling enabled by the transferred charge from the substrate to the MoS2 overlayer, and in part to a stronger MoS2-metal interface by the hydrogen adsorption. These findings may prove to be instrumental in future design of MoS2-based electronics, as well as in exploring novel catalysts for hydrogen production and related chemical processes.},
	author = {Chen, Wei and Elton J. G. Santos and Wenguang Zhu and Efthimios Kaxiras and Zhenyu Zhang}
}
@article {53331,
	title = {Multiphysics Simulations: Challenges and Opportunities},
	journal = {International Journal of High Performance Computing Applications},
	volume = {27},
	number = {1},
	year = {2013},
	pages = {4-83},
	abstract = {We consider multiphysics applications from algorithmic and architectural perspectives, where {\textquotedblleft}algorithmic{\textquotedblright} includes both mathematical analysis and computational complexity, and {\textquotedblleft}architectural{\textquotedblright} includes both software and hardware environments. Many diverse multiphysics applications can be reduced, en route to their computational simulation, to a common algebraic coupling paradigm. Mathematical analysis of multiphysics coupling in this form is not always practical for realistic applications, but model problems representative of applications discussed herein can provide insight. A variety of software frameworks for multiphysics applications have been constructed and refined within disciplinary communities and executed on leading-edge computer systems. We examine several of these, expose some commonalities among them, and attempt to extrapolate best practices to future systems. From our study, we summarize challenges and forecast opportunities.},
	author = {David E. Keyes and Lois Curfman McInnes and Carol Woodward and William Gropp and Eric Myra and et al.}
}
@article {53296,
	title = {Ab initio determination of coarse-grained interactions in double-stranded DNA},
	journal = {Journal of Chemical Physics},
	volume = {137},
	year = {2012},
	pages = {105102},
	abstract = {We derive the coarse-grained interactions between\&nbsp;DNA\&nbsp;nucleotides from\&nbsp;ab initio\&nbsp;total-energy calculations based on\&nbsp;density functional theory\&nbsp;(DFT).\&nbsp;The interactions take into account base and sequence specificity, and are decomposed into physically distinct contributions that includehydrogen bonding,\&nbsp;stacking interactions, backbone, and backbone-base interactions. The interaction\&nbsp;energies\&nbsp;of each contribution are calculated from\&nbsp;DFT\&nbsp;for a wide range of configurations and are fitted by simple analytical expressions for use in the coarse-grained model, which reduces each nucleotide into two sites. This model is not derived from experimental data, yet it successfully reproduces the stable B-DNA\&nbsp;structure\&nbsp;and gives good predictions for the persistence length. It may be used to realistically probe dynamics of\&nbsp;DNA\&nbsp;strands in various environments at the μs time scale and the μm length scale.},
	author = {Chia Wei Hsu and Maria Fyta and Greg Lakatos and Simone Melchionna and Efthimios Kaxiras}
}
@article {53316,
	title = {Concurrent Reaction and Plasticity during Initial Lithiation of Crystalline Silicon in Lithium-Ion Batteries},
	journal = {Journal of the Electrochemical Society},
	volume = {159},
	number = {3},
	year = {2012},
	pages = {A238-A243},
	abstract = {In an electrochemical cell, crystalline silicon and lithium react at room temperature, forming an amorphous phase of lithiated silicon. The reaction front{\textemdash}the phase boundary between the crystalline silicon and the lithiated silicon{\textemdash}is atomically sharp. Evidence has accumulated recently that the velocity of the reaction front is limited by the rate of the reaction at the front, rather than by the diffusion of lithium through the amorphous phase. This paper presents a model of concurrent reaction and plasticity. We identify the driving force for the movement of the reaction front, and accommodate the reaction-induced volumetric expansion by plastic deformation of the lithiated silicon. The model is illustrated by an analytical solution of the co-evolving reaction and plasticity in a spherical particle. We derive the conditions under which the lithiation-induced stress stalls the reaction. We show that fracture is averted if the particle is small and the yield strength of lithiated silicon is low. Furthermore, we show that the model accounts for recently observed lithiated silicon of anisotropic morphologies},
	author = {Kejie Zhao and Matt Pharr and Qiang Wan and Wei L. Wang and Efthimios Kaxiras and Joost J. Vlassak and Zhigang Suo}
}
@article {53216,
	title = {Diffusion of Lithium in Bulk Amorphous Silicon: A Theoretical Study},
	journal = {Journal of Physical Chemistry C},
	volume = {116},
	year = {2012},
	pages = {22212-22216},
	abstract = {The rate performance of lithium-ion secondary batteries depends critically on the kinetic transport of Li within the anode material. Here we use first-principles theoretical calculations to study the diffusion of Li in the low-concentration limit, using model electrodes of crystalline and four-fold coordinated bulk amorphous silicon. We identify Li diffusion pathways that have relatively low energy barriers (\&lt;0.50 eV) in amorphous silicon and discuss how diffusion at short (\~{}2.5 {\r A}), intermediate (\~{}10 {\r A}), and long (\&gt;1 nm) distances depends on the atomic-scale features of the silicon host. We find that both the energy barriers for diffusion and the topology of the atomic structure control the diffusion. We estimate the diffusion rate in amorphous Si anode to be comparable to the rate in crystalline Si anodes. These findings shed light on the wide range of reported experimental results for Li diffusion in Si anodes.},
	author = {Georgios A. Tritsaris and Kejie Zhao and Onyekwelu U. Okeke and Efthimios Kaxiras}
}
@article {53311,
	title = {Identification of defects at the interface between 3C-SiC quantum dots and a SiO2 embedding matrix},
	journal = {Physica Status Solidi},
	volume = {B 249},
	number = {2},
	year = {2012},
	pages = {360-367},
	abstract = {Due to the favorable band offsets, SiC nanoparticles embedded in silica form a very interesting quantum dot (QD) system. It is possible to produce such QDs in a simple oxidation{\textendash}carbonization{\textendash}reoxidation process on Si wafers. This could thus enable production of Si based LED integrated into Si logic devices. However, the luminescence of these QDs, is quenched. This is attributed to defect-mediated recombination of electron{\textendash}hole pairs, most probably at the SiC/SiO2 interface. We present tight-binding simulated annealing calculations, in order to construct models of SiC QDs in SiO2, with the aim of obtaining an overview of the possible defects at the SiC/SiO2 interface. We identify a number of recurring interface defects which can be attributed to C or Si rich conditions or general lattice mismatch relaxation. Similar to defects have been shown to be electrically active at the SiC/SiO2 interface in MOS structures. We find evidence for strained Si{\textendash}Si bonds, which can act as recombination centers in isolated SiC QDs. The defect classes identified in this work can serve as the basis for future, high precision simulations of their electronic structure.},
	author = {Marton Voros and Adam Gali and Efthimios Kaxiras and Thomas Frauenheim and Jan M. Knaup}
}
@article {53301,
	title = {Multiscale Hemodynamics Using GPU Clusters},
	journal = {Communications in Computer Physics},
	volume = {11},
	number = {1},
	year = {2012},
	pages = {48-64},
	abstract = {The parallel implementation of MUPHY, a concurrent multiscale code for large-scale hemodynamic simulations in anatomically realistic geometries, for multiGPU platforms is presented. Performance tests show excellent results, with a nearly linear parallel speed-up on up to 32GPUs and a more than tenfold GPU/CPU acceleration, all across the range of GPUs. The basic MUPHY scheme combines a hydrokinetic (Lattice Boltzmann) representation of the blood plasma, with a Particle Dynamics treatment of suspended biological bodies, such as red blood cells. To the best of our knowledge, this represents the first effort in the direction of laying down general design principles for multiscale/physics parallel Particle Dynamics applications in non-ideal geometries. This configures the present multi-GPU version of MUPHY as one of the first examples of a high-performance parallel code for multiscale/physics biofluidic applications in realistically complex geometries.},
	author = {Mauro Bisson and Massimo Bernaschi and Simone Melchionna and Sauro Succi and Efthimios Kaxiras}
}
@article {53221,
	title = {Optical and elastic properties of diamond-like carbon with metallic inclusions: A theoretical study},
	journal = {Journal of Applied Physics},
	volume = {112},
	year = {2012},
	pages = {103503},
	abstract = {A tough material commonly used in coatings is diamond-like carbon (DLC), that is, amorphous carbon with content in four-fold coordinated C higher than \~{}70\%, and its composites with metal inclusions. This study aims to offer useful guidelines for the design and development of metal-containing DLC coatings for solar collectors, where the efficiency of the collector depends critically on the performance of the absorber coating. We use first-principles calculations based on density functional theory to study the structural, electronic, optical, and elastic properties of DLC and its composites with Ag and Cu inclusions at 1.5\% and 3.0\% atomic concentration, to evaluate their suitability for solar thermal energy harvesting. We find that with increasing metal concentration optical absorption is significantly enhanced while at the same time, the composite retains good mechanical strength: DLC with 70{\textendash}80\% content in four-fold coordinated C and small metal concentrations (\&lt;3 at. \%) will show high absorption in the visible (absorption coefficients higher than 105 cm-1) and good mechanical strength (bulk and Young{\textquoteright}s modulus higher than 300 and 500 GPa, respectively).},
	author = {Georgios A. Tritsaris and Christos Mathioudakis and Pantelis C. Kelires and Efthimios Kaxiras}
}
@article {53321,
	title = {Structural Role of RKS Motifs in Chromatin Interactions: A Molecular Dynamics Study of HP1 Bound to a Variably Modified Histone Tail},
	journal = {Biophysical Journal},
	volume = {102},
	year = {2012},
	pages = {1926-1933},
	abstract = {The current understanding of epigenetic signaling assigns a central role to post-translational modifications that occur in the histone tails. In this context, it has been proposed that methylation of K9 and phosphorylation of S10 in the tail of histone H3 represent a binary switch that controls its reversible association to heterochromatin protein 1 (HP1). To test this hypothesis, we performed a comprehensive molecular dynamics study in which we analyzed a crystallographically defined complex that involves the HP1 chromodomain and an H3 tail peptide. Microsecond-long simulations show that the binding of the trimethylated K9 H3 peptide in the aromatic cage of HP1 is only slightly affected by S10 phosphorylation, because the modified K9 and S10 do not interact directly with one another. Instead, the phosphate group of S10 seems to form a persistent intramolecular salt bridge with R8, an interaction that can provoke a major structural change and alter the hydrogen-bonding regime in the H3-HP1 complex. These observations suggest that interactions between adjacent methyl-lysine and phosphoserine side chains do not by themselves provide a binary switch in the H3-HP1 system, but arginine-phosphoserine interactions, which occur in both histones and nonhistone proteins in the context of a conserved RKS motif, are likely to serve a key regulatory function.},
	author = {George V. Papamokos and George Tziatzos and Dimitrios G. Papageorgiou and Spyros D. Georgatos and Anastasia S. Politou and Efthimios Kaxiras}
}
@article {53211,
	title = {Sulfur-induced embrittlement of nickel: a first-principles study},
	journal = {Modeling and Simulation in Materials Science and Engineering},
	volume = {20},
	year = {2012},
	pages = {065007},
	abstract = {We study the embrittlement of Ni due to the presence of S impurities, considering their effect in the bulk and at grain boundaries (GBs). For bulk Ni, we employ Rice{\textquoteright}s theory based on generalized-stacking-fault energetics and the unstable stacking energy criterion. We use first-principles density-functionaltheory calculations to determine the ductility parameter D = γs/γus, the ratio of the surface energy γs to the unstable stacking energy γus, for bulk Ni with substitutional S impurities. Similar arguments based on Rice{\textquoteright}s theory for the mechanical properties of GBs are invoked. We study the 5(012) GB with interstitial S impurities, in which case D is defined as the ratio of the work of separation Ws and the unstable stacking energy γus, to model the competition between grain decohesion and shear-induced plastic deformation due to grain boundary sliding (GBS). The presence of S impurities is found to increase the value of D by \~{}40\% in bulk Ni, but reduces it by over 80\% for the GB. These results support earlier suggestions that embrittlement of Ni by S impurities is related to their effect on GBs. We further calculate relevant tensile and shear stresses to study the expected fracture mode and find that intergranular crack propagation accommodated by GBS is inhibited in the system considered here.},
	author = {Georg Schusteritsch and Efthimios Kaxiras}
}
@article {50651,
	title = {Direct Imaging of Atomic-Scale Ripples in Few-Layer Graphene},
	journal = {NanoLetters},
	volume = {12},
	year = {2012},
	pages = {2278-2282},
	abstract = {Graphene has been touted as the prototypical two-dimensional solid of extraordinary stability and strength. However, its very existence relies on out-of-plane ripples as predicted by theory and confirmed by experiments. Evidence of the intrinsic ripples has been reported in the form of broadened diffraction spots in reciprocal space, in which all spatial information is lost. Here we show direct real-space images of the ripples in a few-layer graphene (FLG) membrane resolved at the atomic scale using monochromated aberrationcorrected transmission electron microscopy (TEM). The thickness of FLG amplifies the weak local effects of the ripples, resulting in spatially varying TEM contrast that is unique up to inversion symmetry. We compare the characteristic TEM contrast with simulated images based on accurate first-principles calculations of the scattering potential. Our results characterize the ripples in real space and suggest that such features are likely common in ultrathin materials, even in the nanometer-thickness range.},
	author = {Wei L. Wang and Sagar Bhandari and Wei Yi and David C. Bell and Robert Westervelt and Efthimios Kaxiras}
}
@article {50656,
	title = {Reactive Flow in Silicon Electrodes Assisted by the Insertion of Lithium},
	journal = {NanoLetters},
	volume = {12},
	year = {2012},
	pages = {4397-4403},
	abstract = {In the search for high-energy density materials for Li-ion batteries, silicon has emerged as a promising candidate for anodes due to its ability to absorb a large number of Li atoms. Lithiation of Si leads to large deformation and concurrent changes in its mechanical properties, from a brittle material in its pure form to a material that can sustain large inelastic deformation in the lithiated form. These remarkable changes in behavior pose a challenge to theoretical treatment of the material properties. Here, we provide a detailed picture of the origin of changes in the mechanical properties, based on first-principles calculations of the atomic-scale structural and electronic properties in a model amorphous silicon (a-Si) structure. We regard the reactive flow of lithiated silicon as a nonequilibrium process consisting of concurrent Li insertion driven by unbalanced chemical potential and flow driven by deviatoric stress. The reaction enables the material to flow at a lower level of stress. Our theoretical model is in excellent quantitative agreement with experimental measurements of lithiation-induced stress on a Si thin film.},
	author = {Kejie Zhao and Georgios A. Tritsaris and Matt Pharr and Wei L. Wang and Onyekwelu Okeke and Zhigang Suo and Joost J. Vlassak and Efthimios Kaxiras}
}
@article {50661,
	title = {Theoretical Investigation of the C60/Copper Phthalocyanine Organic Photovoltaic Heterojunction},
	journal = {Nano Research},
	volume = {5},
	year = {2012},
	pages = {248-257},
	abstract = {Molecular heterojunctions, such as the one based on copper phthalocyanine (CuPc) and carbon fullerene (C60) molecules, are commonly employed in organic photovoltaic cells as electron donor{\textendash}acceptor pairs. We have investigated the different atomic structures and electronic and optical properties of the C60/CuPc heterojunction through first-principles calculations based on density functional theory (DFT) and time-dependent DFT. In general, configurations with the CuPc molecule {\textquotedblleft}lying down{\textquotedblright} on C60 are energetically more favorable than configurations with the CuPc molecule {\textquotedblleft}standing up{\textquotedblright}. The lying-down configurations also facilitate charge transfer between the two molecules, due to the stronger interaction and the larger overlap between electronic wavefunctions at the interface. The energetically preferred structure consists of CuPc placed so that the Cu atom is above a bridge site of C60, with one N{\textendash}Cu{\textendash}N bond of CuPc being parallel to a C{\textendash}C bond of C60. We also considered the structure of a periodic CuPc monolayer deposited on the (001) surface of a face-centered cubic (fcc) crystal of C60 molecules with the lying-down orientation and on the (111) surface with the standing-up configuration. We find that the first arrangement can lead to larger open circuit voltage due to an enhanced electronic interaction between CuPc and C60 molecules.\&nbsp;},
	author = {Jun Ren and Sheng Meng and Efthimios Kaxiras}
}
@article {230,
	title = {Graphene Structures at an ExtremeDegree of Buckling},
	journal = {ACSNano.},
	volume = {5},
	year = {2011},
	pages = {1395},
	author = {Youdong Mao and Wei L. Wang and Dongguang Wei and Efthimios Kaxiras and Joseph G. Sodroski}
}
@article {233,
	title = {Properties of copper (fluoro-)phthalocyanine layers depositedon epitaxial graphene},
	journal = {J. Chem. Phys.},
	volume = {134},
	year = {2011},
	pages = {194706},
	author = {Jun Ren and Sheng Meng and Yi-Lin Wang and Xu-Cun Ma and Qi-Kun Xue and Efthimios Kaxiras}
}
@article {231,
	title = {Role of defects in propene adsorption and reaction on a partiallyO-covered Au(111) surface},
	journal = {Catal. Sci. Technol.},
	volume = {1},
	year = {2011},
	pages = {1166},
	author = {Thomas A. Baker and Bingjun Xu and Stephen C. Jensen and Cynthia M. Friend andEfthimios Kaxiras}
}
@article {232,
	title = {The Role of Surface and Subsurface Point Defects for Chemical ModelStudies on TiO2: A First-Principles Theoretical Study of FormaldehydeBonding on Rutile TiO2(110)},
	journal = {Chem. Eur. J.},
	volume = {17},
	year = {2011},
	pages = {4496},
	author = {Jan Haubrich and Efthimios Kaxiras and Cynthia M. Friend}
}
@article {229,
	title = {Stiffening of organosilicate glasses by organic cross-linking},
	journal = {Acta Mater.},
	volume = {59},
	year = {2011},
	pages = {44},
	author = {H. Li and J.M. Knaup and E. Kaxiras and J.J. Vlassak}
}
@article {244,
	title = {Approaching the intrinsic band gap in suspended high-mobility graphene nanoribbons},
	journal = {PHYSICAL REVIEW B},
	volume = {84},
	year = {2011},
	pages = {125411},
	author = {Ming-Wei Lin and Cheng Ling and Luis A. Agapito and Nicholas Kioussis and Yiyang Zhang and Mark Ming-Cheng Cheng and Wei L. Wang and Efthimios Kaxiras and Zhixian Zhou1,}
}
@article {235,
	title = {Design of Dye Acceptors for Photovoltaics from First-PrinciplesCalculations},
	journal = {J. Phys. Chem. C},
	volume = {115},
	year = {2011},
	pages = {9276},
	author = {Sheng Meng and Efthimios Kaxiras and Md. K. Nazeeruddin and Michael Gratzel}
}
@article {241,
	title = {Direct correlation of crystal structure and optical properties in wurtzite/zinc-blendeGaAs nanowire heterostructures},
	journal = {PHYSICAL REVIEW B},
	volume = {83},
	year = {2011},
	pages = {045303},
	author = {Martin Heiss and Sonia Conesa-Boj and Jun Ren and Hsiang-Han Tseng and Adam Gali and Andreas Rudolph and Emanuele Uccelli and Francesca Peiro and Joan Ramon Morante and Dieter Schuh and Elisabeth Reiger and Efthimios Kaxiras and Jordi Arbiol and Anna Fontcuberta i Morral}
}
@article {243,
	title = {Effect of symmetry breaking on the optical absorption of semiconductor nanoparticles},
	journal = {PHYSICAL REVIEW B},
	volume = {84},
	year = {2011},
	pages = {035325},
	author = {JAdam Gali and Efthimios Kaxiras and Gergely T. Zimanyi and Sheng Meng}
}
@article {240,
	title = {Endothelial shear stress from large-scale blood flow simulations},
	journal = {Phil. Trans. R. Soc. A},
	volume = {369},
	year = {2011},
	pages = {2354},
	author = {Simone Melchionna and Efthimios Kaxiras and Massimo Bernaschi and Sauro Succi}
}
@article {242,
	title = {Influence of CH2 content and network defects on the elastic properties of organosilicate glasses},
	journal = {PHYSICAL REVIEW B},
	volume = {83},
	year = {2011},
	pages = {054204},
	author = {Jan M. Knaup and Han Li and Joost J. Vlassak and Efthimios Kaxiras}
}
@article {238,
	title = {Lithium-Assisted Plastic Deformation of Silicon Electrodes inLithium-Ion Batteries: A First-Principles Theoretical Study},
	journal = {Nano Lett.},
	volume = {11},
	year = {2011},
	pages = {2962},
	author = {Kejie Zhao and Wei L. Wang and John Gregoire and Matt Pharr and Zhigang Suo and Joost J. Vlassak and Efthimios Kaxiras}
}
@article {236,
	title = {New Insights into the Structure of the Vapor/WaterInterface from Large-Scale First-Principles Simulations},
	journal = {J. Phys. Chem. Lett.},
	volume = {2},
	year = {2011},
	pages = {105},
	author = {Thomas D. Kuhne and Tod A. Pascal and Efthimios Kaxiras and Yousung Jung}
}
@article {239,
	title = {Properties of nitrogen-vacancy centers in diamond:the group theoretic approach},
	journal = {New Journal of Physics},
	volume = {13},
	year = {2011},
	pages = {025025},
	author = {J R Maze and A Gali and E Togan and Y Chu and A Trifonov and E. Kaxiras and M D Lukin}
}
@article {234,
	title = {Theoretical Study of O-Assisted Selective Coupling of Methanol onAu(111)},
	journal = {J. Phys. Chem. C},
	volume = {115},
	year = {2011},
	pages = {3703},
	author = {Bingjun Xu and Jan Haubrich and Thomas A. Baker and Efthimios Kaxiras and Cynthia M. Friend}
}
@article {340896,
	title = {D-π-A Dye System Containing Cyano-Benzoic Acid as Anchoring Group for Dye-Sensitized Solar Cells},
	journal = {Langmuir},
	volume = {27},
	number = {23},
	year = {2011},
	pages = {14248{\textendash}14252},
	author = {Masataka Katono and Takeru Bessho and Sheng Meng and Robin Humphry-Baker and Guido Rothenberger and Shaik M. Zakeeruddin and Efthimios Kaxiras and Michael Gratzel}
}
@article {53421,
	title = {Design of Dye Acceptors for Photovoltaics from First-Principles Calculations},
	journal = {Journal of Physical Chemistry C},
	volume = {115},
	year = {2011},
	pages = {9276-9282},
	abstract = {We investigate a set of donor-π-acceptor (D-π-A) dyes with new acceptor groups for dye-sensitized solar cells, using time-dependent density-functional-theory calculations of the electronic structure and optical absorption. We considered three types of modifications on existing dye structures: (i) replacement of the side cyano group (CN) on the molecular anchor, (ii) insertion and alteration of the intermediate spacer groups, and (iii) modification of the number and positions of cyano CN groups on a phenyl-ring spacer. We find that with these modifications, the dye electronic levels and corresponding optical absorption properties can be gradually tuned, rendering possible the identification of dyes with desirable structural, electronic, and optical properties. For example, dyes with phenyl and CN-substituted phenyl groups are promising candidates for red light absorption and high molar extinction coefficients.},
	author = {Sheng Meng and Efthimios Kaxiras and Md. K. Nazeeruddin and Michael Graetzel}
}
@article {53431,
	title = {Direct correlation of crystal structure and optical properties in wurtzite/zinc-blende GaAs nanowire heterostructures},
	journal = {Physical Review B},
	volume = {83},
	year = {2011},
	pages = {045303},
	abstract = {A method for the direct correlation at the nanoscale of structural and optical properties of single GaAs nanowires is reported. Nanowires consisting of 100\% wurtzite and nanowires presenting zinc-blende/wurtzite polytypism are investigated by photoluminescence spectroscopy and transmission electron microscopy. The photoluminescence of wurtzite GaAs is consistent with a band gap of 1.5 eV. In the polytypic nanowires, it is shown that the regions that are predominantly composed of either zinc-blende or wurtzite phase show photoluminescence emission close to the bulk GaAs band gap, while regions composed of a nonperiodic superlattice of wurtzite and zinc-blende phases exhibit a redshift of the photoluminescence spectra as low as 1.455 eV. The dimensions of the quantum heterostructures are correlated with the light emission, allowing us to determine the band alignment between these two crystalline phases. Our first-principles electronic structure calculations within density functional theory, employing a hybrid-exchange functional, predict band offsets and effective masses in good agreement with experimental results.},
	author = {Martin Heiss and Sonia Conesa-Boj and Jun Ren and Hsiang-Han Tseng and Adam Gali and Andreas Rudolph and Emanuele Uccelli and Francesca Peiro and Joan Ramon Morante and Dieter Schuh and Elisabeth Reiger and Efthimios Kaxiras and Jordi Arbiol and Anna Fontcuberta i Morral}
}
@article {53396,
	title = {D-π-A Dye System Containing Cyano-Benzoic Acid as Anchoring Group for Dye-Sensitized Solar Cells},
	journal = {Langmuir},
	volume = {27},
	year = {2011},
	pages = {14248-14252},
	abstract = {A D-π-A dye (KM-1) incorporating cyanobenzoic acid as a new acceptor/anchoring group has been synthesized for dye-sensitized solar cells (DSCs) with a high molar extinction coefficient of 66 700 M-1 cm-1 at 437 nm. Theoretical calculations show that the hydrogen bond between CN and surface hydroxyl leads to the most stable configuration on the surface of TiO2. In addition, the adsorption of the dye on TiO2 follows a BrunauerEmmettTeller (BET) isotherm. Multilayer adsorption of KM-1 on TiO2 seems to take place particularly at higher dye concentrations. DSC device using KM-1 reached a maximum incident photon-to-current conversion efficiency (IPCE) of 84\%, with a solar to electric power conversion efficiency (PCE) of 3.3\% at AM1.5 G illumination (100 mW cm-2 ). This new type of anchoring group paves a way to design new dyes that combine good visible light harvesting with strong binding to the metal oxide surface},
	author = {Masataka Katono and Takeru Bessho and Sheng Meng and Robin Humphry-Baker and Guido Rothenberger and Shaik M. Zakeeruddin and Efthimios Kaxiras and Michael Graetzel}
}
@article {53411,
	title = {Endothelial shear stress from large-scale blood flow simulations},
	journal = {Philosophical Transactions of the Royal Society A},
	volume = {369},
	year = {2011},
	pages = {2354-2361},
	abstract = {
We discuss the optimal evaluation of endothelial shear stress for real-life case studies based on anatomic data acquisition. The fluid dynamic simulations require smoothing of the geometric dataset to avoid major artefacts in the flow patterns, especially in the proximity of bifurcations. A systematic series of simulations at different corrugation levels shows that, below a smoothing length of about 0.5 mm, the numerical data are insensitive to further smoothing.

},
	author = {Simone Melchionna and Efthimios Kaxiras and Massimo Bernaschi and Sauro Succi}
}
@article {53436,
	title = {Graphene Structures at an Extreme Degree of Buckling},
	journal = {ACS Nano},
	volume = {5},
	number = {2},
	year = {2011},
	pages = {1395-1400},
	abstract = {T The distinctive properties of graphene sheets may be significantly influenced by the presence of corrugation structures. Our understanding of these graphene structures has been limited to the mesoscopic scale. Here we characterize angstrom-scale periodic buckling structures in freestanding graphene bilayers produced by liquid-phase processing in the absence of specific substrates. Monochromated, aberration-corrected transmission electron microscopy with sub-angstrom resolution revealed that the unit structures in the major buckling direction consist of only two and three unit cells of graphene{\textquoteright}s honeycomb lattice, resulting in buckling wavelengths of 3.6{\textpm}0.5 and 6.4{\textpm}0.8 {\r A}, respectively. The buckling shows a strong preference of chiral direction and spontaneously chooses the orientation of the lowest deformation energy, governed by simple geometry rules agreeing with Euler buckling theory. Unexpectedly, the overall buckled structures demonstrate geometric complexity with cascaded features. First-principles calculations suggest that significant anisotropic changes in the electronic structure of graphene are induced by the buckling.},
	author = {Youdong Mao and Wei L. Wang and Dongguang Wei and Efthimios Kaxiras and Joseph G. Sodroski}
}
@article {53441,
	title = {Influence of CH2 content and network defects on the elastic properties of organosilicate glasses},
	journal = {Physical Review B},
	volume = {83},
	year = {2011},
	pages = {054204},
	abstract = {Organosilicate glasses (OSGs) are used as low-k intermetal dielectrics for advanced integrated circuits. In this application, the material must fulfill two conflicting requirements: It has to have low density to reduce the dielectric constant while being sufficiently mechanically stable to withstand thermomechanical and other stresses during subsequent steps of integrated circuit manufacture. Recent experimental advances in improving the mechanical and electrical properties of these materials have not yet been systematically studied theoretically at the ab initio level due to the large model sizes necessary to realistically describe amorphous materials. In this paper we employ the density-functional-based tight-binding method to achieve an accurate description of OSG properties at different compositions. We analyze the influence of composition and local network defects on the density and bulk modulus of nonporous OSG. We find that the dependence of density and that of mechanical stiffness on chemical composition are of different natures. This difference is traced to a transition between mechanisms of elastic deformation in silica glass and in silicon hydrocarbide, which is also the reason for the two materials{\textquoteright} different sensitivities to network defects.},
	author = {Jan M. Knaup and Han Li and Joost J. Vlassak and Efthimios Kaxiras}
}
@article {53401,
	title = {Lithium-Assisted Plastic Deformation of Silicon Electrodes in Lithium-Ion Batteries: A First-Principles Theoretical Study},
	journal = {NanoLetters},
	volume = {11},
	year = {2011},
	pages = {2962-2967},
	abstract = {Silicon can host a large amount of lithium, making it a promising electrode for high-capacity lithium-ion batteries. Recent experiments indicate that silicon experiences large plastic deformation upon Li absorption, which can significantly decrease the stresses induced by lithiation and thus mitigate fracture failure of electrodes. These issues become especially relevant in nanostructured electrodes with confined geometries. On the basis of first-principles calculations, we present a study of the microscopic deformation mechanism of lithiated silicon at relatively low Li concentration, which captures the onset of plasticity induced by lithiation. We find that lithium insertion leads to breaking of SiSi bonds and formation of weaker bonds between neighboring Si and Li atoms, which results in a decrease in Young{\textquoteright}s modulus, a reduction in strength, and a brittle-to-ductile transition with increasing Li concentration. The microscopic mechanism of large plastic deformation is attributed to continuous lithium-assisted breaking and re-forming of SiSi bonds and the creation of nanopores.},
	author = {Kejie Zhao and Wei L. Wang and John Gregoire and Matt Pharr and Zhigang Suo and Joost J. Vlassak and Efthimios Kaxiras}
}
@article {53446,
	title = {New Insights into the Structure of the Vapor/Water Interface from Large-Scale First-Principles Simulations},
	journal = {Journal of Physical Chemistry Letters},
	volume = {2},
	year = {2011},
	pages = {105-113},
	abstract = {We present extensive ab initio simulations of the molecular arrangements at the vapor/water interface, which provide valuable insights into the interface structure. In particular, the simulations address the controversy of whether there is a significant amount of nondonor configurations at this prototypical interface, using a novel Car-Parrinello-like ab initio molecular dynamics approach. The interface is modeled by a system of 384 water molecules for 125 ps in a two-dimensional periodic slab, the most extensive ab initio molecular dynamics simulation to date. In contrast to previous theoretical simulations and X-ray absorption spectroscopy, but consistent with sum-frequency generation experiments, we observe no evidence for a significant occurrence of acceptoronly species at the vapor/water interface. Besides a distinct surface relaxation effect, we find that only the topmost layers of the interface obey structural order.},
	author = {Thomas D. Kuehne and Tod A. Pascal and Efthimios Kaxiras and Yousung Jung}
}
@article {53406,
	title = {Properties of copper (fluoro-)phthalocyanine layers deposited on epitaxial graphene},
	journal = {Journal of Chemical Physics},
	volume = {134},
	year = {2011},
	pages = {194706},
	abstract = {We investigate the atomic structure and electronic properties of monolayers of copper phthalocyanines (CuPc) deposited on epitaxial graphene substrate. We focus in particular on hexadecafluorophthalocyanine (F16CuPc), using both theoretical and experimental (scanning tunneling microscopy {\textendash} STM) studies. For the individual CuPc and F16CuPc molecules, we calculated the electronic and optical properties using density functional theory (DFT) and time-dependent DFT and found a red-shift in the absorption peaks of F16CuPc relative to those of CuPc. In F16CuPc, the electronic wavefunctions are more polarized toward the electronegative fluorine atoms and away from the Cu atom at the center of the molecule. When adsorbed on graphene, the molecules lie flat and form closely packed patterns: F16CuPc forms a hexagonal pattern with two well-ordered alternating α and β stripes while CuPc arranges into a square lattice. The competition between molecule-substrate and intermolecular van der Waals interactions plays a crucial role in establishing the molecular patterns leading to tunable electron transfer from graphene to the molecules. This transfer is controlled by the layer thickness of, or the applied voltage on, epitaxial graphene resulting in selective F16CuPc adsorption, as observed in STM experiments. In addition, phthalocyanine adsorption modifies the electronic structure of the underlying graphene substrate introducing intensity smoothing in the range of 2{\textendash}3 eV below the Dirac point (ED) and a small peak in the density of states at \~{}0.4 eV above ED.},
	author = {Jun Ren and Sheng Meng and Yi-Lin Wang and Xu-Cun Ma and Qi-Kun Xue and Efthimios Kaxiras}
}
@article {53451,
	title = {Properties of nitrogen-vacancy centers in diamond: the group theoretic approach},
	journal = {New Journal of Physics},
	volume = {13},
	year = {2011},
	pages = {025025},
	abstract = {We present a procedure that makes use of group theory to analyze and predict the main properties of the negatively charged nitrogen-vacancy (NV) center in diamond. We focus on the relatively low temperature limit where both the spin{\textendash}spin and spin{\textendash}orbit effects are important to consider. We demonstrate that group theory may be used to clarify several aspects of the NV structure, such as ordering of the singlets in the (e 2 ) electronic configuration and the spin{\textendash}spin and spin{\textendash}orbit interactions in the (ae) electronic configuration. We also discuss how the optical selection rules and the response of the center to electric field can be used for spin{\textendash}photon entanglement schemes. Our general formalism is applicable to a broad class of local defects in solids. The present results have important implications for applications in quantum information science and nanomagnetometry.},
	author = {J R Maze and A Gali and E Togan and Y Chu and A Trifonov and Efthimios Kaxiras and M D Lukin}
}
@article {53391,
	title = {Role of defects in propene adsorption and reaction on a partially O-covered Au(111) surface},
	journal = {Catalysis Science \& Technology},
	volume = {1},
	year = {2011},
	pages = {1166-1174},
	abstract = {We investigate the role of defects{\textemdash}adatoms, vacancies, and steps{\textemdash}in the bonding and reaction of propene on Au(111) containing atomic oxygen, using density functional theory (DFT) calculations. The adsorption of propene is stronger on a surface containing defects compared to the flat, bulk-terminated surface, with the largest gain in binding (~0.7 eV) on a surface with a 1/9 monolayer (ML) of Au adatoms. Charge-density difference plots reveal that the difference between defective surfaces and the bulk-terminated surface is a more pronounced depletion of electron density from the carbon{\textendash}carbon p bond and a charge accumulation between the double bond and the gold atom to which the propene is bound. We calculate the energy barriers for two competing reactions that are important in determining the selectivity for propene oxidation. Allylic H abstraction by adsorbed O leads to combustion, whereas O addition to form an oxymetallacycle is the first step in propene epoxide formation. A comparison of the energetics of these two pathways on flat and defect-containing Au surfaces indicates that the reactivity depends on the nature and prevalence of surface defects. Both electronic and geometric factors, such as the path and the distance the oxygen must travel to meet the allylic hydrogen for abstraction, are important in explaining the reaction trends.},
	author = {Thomas A. Baker and Bingjun Xu and Stephen C. Jensen and Cynthia M. Friend and Efthimios Kaxiras}
}
@article {53416,
	title = {The Role of Surface and Subsurface Point Defects for Chemical Model Studies on TiO2: A First-Principles Theoretical Study of Formaldehyde Bonding on Rutile TiO2(110)},
	journal = {Chemistry - a European Journal},
	volume = {17},
	year = {2011},
	pages = {4496-4506},
	abstract = {We report a systematic investigation of the effects of different surface and subsurface point defects on the adsorption of formaldehyde on rutile TiO2(110) surfaces using density functional theory (DFT). All point defects investigated{\textemdash}including surface bridging oxygen vacancies, titanium interstitials, and subsurface oxygen vacancies{\textemdash}stabilize the adsorption significantly by up to 56 kJ mol-1 at a coverage of 0.1 monolayer (ML). The stabilization is due to a decrease of the coordination (covalent saturation) of the surface Ti adsorption sites adjacent to the defects, which leads to a stronger molecule{\textendash}surface interaction. This change in the Ti is caused by the removal of a neighboring atom (oxygen vacancies) or substantial lattice relaxations induced by the subsurface defects. On the stoichiometric reference surface, the most stable adsorption geometry of formaldehyde is a tilted η2 -dioxymethylene (with an adsorption energy Eads=-125 kJ mol-1 ), in which a bond forms to a nearby bridging O atom and the carbonyl-O atom in the formaldehyde binds to a Ti atom in the adjacent fivefold coordinated lattice site. The η1 -top configuration on fivecoordinate Ti4+ is much less favorable (Eads=-69 kJ mol-1 ). The largest stabilization is exerted by subsurface Ti interstitials between the first and second layers. These defects stabilize the η2 -dioxymethylene structure by nearly 40 kJ mol-1 to an adsorption energy of 164 kJ mol-1 . Contrary to popular belief, adsorption in a bridging oxygen vacancy (Eads=-86 kJ mol-1 ) is much less favorable for formaldehyde compared to the η2 - dioxymethylene structures. From these results we conclude that formaldehyde will bind in the η2\&nbsp;- dioxymethylene structure on the stoichiometric surface as well as in the presence of Ti interstitials and bridging oxygen vacancies. In the light of these substantial effects, we conclude that it is essential to include all the types of point defects present in typical, reduced rutile samples used for model studies, at realistic concentrations to obtain correct adsorption sites, structures, energetic, and chemi-physical properties.\&nbsp;},
	author = {Jan Haubrich and Efthimios Kaxiras and Cynthia M. Friend}
}
@article {53461,
	title = {Stiffening of organosilicate glasses by organic cross-linking},
	journal = {Acta Materialia},
	volume = {59},
	year = {2011},
	pages = {44-52},
	abstract = {Atomistic simulations show that organosilicates, used as low permittivity dielectric materials in advanced integrated circuits, can be made substantially stiffer than amorphous silica, while maintaining a lower mass density. The enhanced stiffness is achieved by incorporating organic cross-links to replace bridging oxygen atoms in the silica network. To elucidate the mechanism responsible for the enhanced stiffness, the conformational changes in the network upon hydrostatic and shear loading are examined. The structural and mechanical impact of terminal methyl groups is also assessed quantitatively and compared with continuous random network theory.},
	author = {Han Li and Jan M. Knaup and Efthimios Kaxiras and Joost J. Vlassak}
}
@article {53426,
	title = {Theoretical Study of O-Assisted Selective Coupling of Methanol on Au(111)},
	journal = {Journal of Physical Chemistry C},
	volume = {115},
	year = {2011},
	pages = {3703-3708},
	abstract = {We report the first systematic theoretical study of the oxidative self-coupling of methanol to form the ester, methylformate, on atomic-oxygen-covered Au(111) using density functional theory calculations. The first step in the process {\textemdash}dissociation of the O-H bond in methanol{\textemdash}has a lower barrier for transfer of the proton to adsorbed oxygen than for transfer of H to gold, consistent with experimental observations that O is necessary to initiate the reaction. The computed barrier for formation of methoxy (CH3O) and OH is 0.41 eV, compared with 1.58 eV calculated for the transfer of H to the clean Au surface. Several different pathways for the ensuing β-H elimination in CH3O(ads) to form formaldehyde have been considered, namely, attack by adsorbed O, OH, or a second CH3O, and transfer to the Au metal. Methoxy attacked by surface oxygen has the lowest calculated barrier, 0.49 eV, and leads to adsorbed H2C=O and OH. Subsequent coupling of methoxy and formaldehyde has no apparent barrier in the calculation, consistent with the experimental conclusion that β-H elimination is the rate-limiting step for the overall reaction. With the exception of surface oxygen, all other surface species have low diffusion barriers, suggesting that rearrangement and movement of these species from the preferred adsorption sites to configurations necessary for reactions occur readily, thus contributing to the activity for coupling on gold.},
	author = {Bingjun Xu and Jan Haubrich and Thomas A. Baker and Efthimios Kaxiras and Cynthia M. Friend}
}
@article {50741,
	title = {Approaching the intrinsic band gap in suspended high-mobility graphene nanoribbons},
	journal = {Physical Review B},
	volume = {84},
	year = {2011},
	pages = {125411},
	abstract = {We report electrical transport measurements on a suspended ultra-low-disorder graphene nanoribbon (GNR) with nearly atomically smooth edges that reveal a high mobility exceeding 3000 cm2 V-1 s-1 and an intrinsic band gap. The experimentally derived band gap is in quantitative agreement with the results of our electronic structure calculations on chiral GNRs with comparable width taking into account the electron-electron interactions, indicating that the origin of the band gap in nonarmchair GNRs is partially due to the magnetic zigzag edges},
	author = {Ming-Wei Lin and Cheng Ling and Luis A. Agapito and Nicholas Kioussis and Yiyang Zhang and Mark Ming-Cheng Cheng and Wei L. Wang and Efthimios Kaxiras and Zhixian Zhou}
}
@article {50736,
	title = {Effect of symmetry breaking on the optical absorption of semiconductor nanoparticles},
	journal = {Physical Review B},
	volume = {84},
	year = {2011},
	pages = {035325},
	abstract = {The shape of semiconductor nanoparticles (NPs) can have an important influence on their optical absorption spectra with enhanced absorption resulting from breaking their symmetries. To illustrate this effect, we present broad energy optical excitation spectra of \~{}2 nm Si and PbSe nanoparticles, obtained from extensive timedependent density functional theory calculations. We considered both highly symmetric spherical shapes and low-symmetry rodlike and disklike shapes. The low-symmetry shapes exhibit an increase in absorption at low and relatively high energies compared to the absorption of spherical NPs of similar volume, independent of their chemical compositions and surface structures. Our results elucidate the mechanism of enhanced multiexciton generation in semiconductor NPs, which is important in the quest to improve their photovoltaic applications.},
	author = {Adam Gali and Efthimios Kaxiras and Gergely T. Zimanyi and Sheng Meng}
}
@article {221,
	title = {Compositional tuning of ultrathin surface oxides on metal and alloysubstrates using photons: Dynamic simulations and experiments},
	journal = {Phys. Rev. B},
	volume = {81},
	year = {2010},
	pages = {085406},
	author = {C.L. Chang and S.K.R.S. Sankaranarayanan and D. Ruzmetov and M.H. Engelhard and E. Kaxiras and S. Ramanathan}
}
@article {222,
	title = {Electron and Hole Dynamics in Dye-Sensitized Solar Cells:Influencing Factors and Systematic Trends},
	journal = {NanoLett.},
	volume = {10},
	year = {2010},
	pages = {1238},
	author = {S. Meng and E. Kaxiras}
}
@article {223,
	title = {Embrittlement of Metal by Solute Segregation-Induced Amorphization},
	journal = {Phys. Rev. Lett.},
	volume = {104},
	year = {2010},
	pages = {155502},
	author = {H.P. Chen and R.K. Kalia and E. Kaxiras and G. Lu and A. Nakano and K. Nomura and A.C.T. van Duin and P. Vashishta and Z.S. Yuan}
}
@article {218,
	title = {A flexible high-performance Lattice Boltzmann GPU code for thesimulations of fluid flows in complex geometries},
	journal = {Concurrency Computat.: Pract. Exper.},
	volume = {22},
	year = {2010},
	pages = {1},
	author = {M. Bernaschi and M. Fatica and S. Melchionna and S. Succi and E. Kaxiras}
}
@article {219,
	title = {Hydrokinetic approach to large-scale cardiovascular blood flow},
	journal = {Comp. Phys. Comm.},
	volume = {181},
	year = {2010},
	pages = {462},
	author = {S. Melchionna and M. Bernaschi and S. Succi and E. Kaxiras and F.J. Rybicki and D. Mitsouras and A.U. Coskun and C.L. Feldman}
}
@article {220,
	title = {Local Bonding Effects in the Oxidation of CO on Oxygen-CoveredAu(111) from Ab Initio Molecular Dynamics Simulations},
	journal = {J. Chem. Theory Comput.},
	volume = {6},
	year = {2010},
	pages = {279},
	author = {T.A. Baker and C.M. Friend and E. Kaxiras}
}
@article {217,
	title = {Is the nature of magnetic order in copper-oxides and iron-pnictides different?},
	journal = {Sol. St. Comm.},
	volume = {150},
	year = {2010},
	pages = {62},
	author = {E. Manousakis and J. Ren and S. Meng and E. Kaxiras}
}
@article {227,
	title = {Electric-field control of magnetism in graphene quantum dots: Ab initio calculations},
	journal = {Phys. Rev. B},
	volume = {82},
	year = {2010},
	pages = {201411},
	author = {L.A. Agapito and N. Kioussis and E. Kaxiras}
}
@article {228,
	title = {Graphene hydrate: theoretical prediction of a new insulating form of graphene},
	journal = {New J. Phys.},
	volume = {12},
	year = {2010},
	pages = {125012},
	author = {W.L. Wang and E. Kaxiras}
}
@article {224,
	title = {Insights from Theory on the Relationship Between Surface Reactivityand Gold Atom Release},
	journal = {Top. Catal.},
	volume = {53},
	year = {2010},
	pages = {365},
	author = {T.A. Baker and E. Kaxiras and C.M. Friend}
}
@article {226,
	title = {Multiscale simulation of cardiovascular flows on the IBM Bluegene : full heart-circulation system at near red-blood cell resolution},
	journal = {2010 ACM/IEEE International Conference for High Performance Computing, Networking, Storage and Analysis},
	volume = {doi: 10.1109/SC.2010.33},
	year = {2010},
	author = {A. Peters and S. Melchionna and E. Kaxiras and J. Latt and J. Sircar and M. Bernaschi and M. Bisson and S. Succi}
}
@article {225,
	title = {Optical properties of clusters and molecules from real-time time-dependentdensity functional theory using a self-consistent field},
	journal = {Molec. Phys.},
	volume = {108},
	year = {2010},
	pages = {1829},
	author = {J. Ren and E. Kaxiras and S. Meng}
}
@article {202,
	title = {Atomic Oxygen Adsorption on Au(111) Surfaces with Defects},
	journal = {J. Phys. Chem. C},
	volume = {113},
	year = {2009},
	pages = {3232},
	author = {T.A. Baker and C.M. Friend and E. Kaxiras}
}
@article {203,
	title = {Effects of chlorine and oxygen coverage on the structure of the Au(111) surface},
	journal = {J. Chem. Phys.},
	volume = {130},
	year = {2009},
	pages = {084701},
	author = {T.A. Baker and C.M. Friend and E. Kaxiras}
}
@article {204,
	title = {Atomistic Simulation of Field Enhanced Oxidation of Al(1000) Beyond the Mott Potential},
	journal = {Phys. Rev. Lett.},
	volume = {102},
	year = {2009},
	pages = {095504},
	author = {S.K.R.S. Sankaranarayanan and E. Kaxiras and S. Ramanathan}
}
@article {206,
	title = {Comment on {\textquoteright}Ab initio Electronic and Optical Properties of the N-V-Center in Diamond{\textquoteright}},
	journal = {Phys. Rev. Lett.},
	volume = {102},
	year = {2009},
	pages = {149703},
	author = {A. Gali and E. Kaxiras}
}
@article {209,
	title = {Control algorithm for multiscale flow simulations of water},
	journal = {Phys. Rev. E - Rap. Comm.},
	volume = {79},
	year = {2009},
	pages = {045701},
	author = {E.M. Kotsalis and J.H. Walther and E. Kaxiras and P. Koumoutsakos}
}
@article {213,
	title = {Nature of Oxidation of the Au(111) Surface: Experiment andTheoretical Investigation},
	journal = {J. Phys. Chem. C},
	volume = {113},
	year = {2009},
	pages = {16561},
	author = {T.A. Baker and B.J. Xu and X.Y. Liu and E. Kaxiras and C.M. Friend}
}
@article {210,
	title = {Numerical simulation of conformational variability in biopolymer translocation through wide nanopores},
	journal = {J. Stat. Mech: Th. and Exper.},
	volume = {06},
	year = {2009},
	author = {M. Fyta and S. Melchionna and M. Bernaschi and E. Kaxiras and S. Succi}
}
@article {211,
	title = {Optimization of Mn doping in group-IV-based dilute magnetic semiconductorsby electronic codopants},
	journal = {Phys. Rev. B},
	volume = {79},
	year = {2009},
	pages = {235202},
	author = {H. Chen and W.G. Zhu and E. Kaxiras and Z.Y. Zhang}
}
@article {212,
	title = {Prediction of coronary artery plaque progression and potential rupturefrom 320-detector row prospectively ECG-gated single heart beat CT angiography: Lattice Boltzmann evaluation of endothelial shear stress},
	journal = {Int. J. Cardiovasc. Imaging},
	volume = {25},
	year = {2009},
	pages = {289},
	author = {F.J. Rybicki and S. Melchionna and D. Mitsouras and A.U. Coskun and A.G. Whitmore and M. Steigner and L. Nallamshetty and F.G. Welt and M. Bernaschi and M. Borkin and J. Sircar and E. Kaxiras and S. Succi and P.H. Stone and C.L. Feldman}
}
@article {205,
	title = {Quantized biopolymer translocation through nanopores: Departure from simple scaling},
	journal = {Phys. Rev. E - Rap. Comm.},
	volume = {79},
	year = {2009},
	pages = {030901},
	author = {S. Melchionna and M. Bernaschi and M. Fyta and E. Kaxiras and S. Succi}
}
@article {208,
	title = {Structural, Electronic, and Optical Properties of Representative Cu-Flavonoid Complexes},
	journal = {J. Phys. Chem. B},
	volume = {113},
	year = {2009},
	pages = {6478},
	author = {C.E. Lekka and J. Ren and S. Meng and E. Kaxiras}
}
@article {207,
	title = {Topological Frustration in Graphene Nanoflakes: Magnetic Order and Spin Logic Devices},
	journal = {Phys. Rev. Lett.},
	volume = {102},
	year = {2009},
	pages = {157201},
	author = {W.L. Wang and O.V. Yazyev and S. Meng and E. Kaxiras}
}
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@article {125,
	title = {Hydrogen bonding and stacking interactions of nucleic acid base pairs: A density-functional-theory based treatment},
	journal = {J. Chem. Phys.},
	volume = {114},
	year = {2001},
	pages = {5149},
	author = {M. Elstner and P. Hobza and T. Frauenheim and S. Suhai and E. Kaxiras}
}
@article {130,
	title = {Multiscale simulation of silicon nanoindentation},
	journal = {Acta Materialia},
	volume = {49},
	year = {2001},
	pages = {4089},
	author = {G.S. Smith and E.B. Tadmor and N. Bernstein and E. Kaxiras}
}
@article {126,
	title = {A QM/MM implementation of the self-consistent charge density functional tight binding (SCC-DFTB) method},
	journal = {J. Phys. Chem. B},
	volume = {105},
	year = {2001},
	pages = {569},
	author = {Cui, Q. and M. Elstner and E. Kaxiras and T. Frauenheim and M. Karplus}
}
@article {127,
	title = {Quantum mechanics simulation of protein dynamics on long timescale},
	journal = {Proteins: Structure, Function and Genetics},
	volume = {44},
	year = {2001},
	pages = {484},
	author = {H. Liu and M. Elstner and E. Kaxiras and Th. Frauenheim and J. Hermans and W. Yang}
}
@article {131,
	title = {Variational finite-difference representation of the kinetic energy operator},
	journal = {Phys. Rev. B},
	volume = {64},
	year = {2001},
	pages = {193101},
	author = {P. Maragakis and J. Soler and E. Kaxiras}
}
@article {113,
	title = {Atomistic simulations of solid-phase epitaxial growth in silicon},
	journal = {Phys. Rev. B},
	volume = {61},
	year = {2000},
	pages = {6696},
	author = {N. Bernstein and M. J. Aziz and E. Kaxiras}
}
@article {112,
	title = {Modeling brittle and ductile behavior of solids from first-principles calculations},
	journal = {Phys. Stat. Sol. B},
	volume = {217},
	year = {2000},
	pages = {545},
	author = {U.V. Waghmare and E. Kaxiras and M.S. Duesbery}
}
@article {111,
	title = {Multiscale simulation of loading and electrical resistance in silicon nanoindentation},
	journal = {Phys. Rev. Lett.},
	volume = {84},
	year = {2000},
	pages = {1260},
	author = {G.S. Smith and E.B. Tadmor and E. Kaxiras}
}
@article {115,
	title = {A density functional theory study of site-specific methyl reaction on MoO>3(010):The effects of methyl coverage},
	journal = {J. Chem. Phys.},
	volume = {112},
	year = {2000},
	pages = {9617},
	author = {M. Chen and C.M. Friend and E. Kaxiras}
}
@article {114,
	title = {Energetic, vibrational and electronic properties of silicon using a nonorthogonal tight-binding model},
	journal = {Phys. Rev. B},
	volume = {62},
	year = {2000},
	pages = {4477},
	author = {N. Bernstein and M.J. Mehl and D.A. Papaconstantopoulos and M.Z. Bazant and E. Kaxiras}
}
@article {118,
	title = {Generalized stacking fault energy surface and dislocation properties of aluminum},
	journal = {Phys. Rev. B},
	volume = {62},
	year = {2000},
	pages = {3099},
	author = {G. Lu and N. Kioussis and V.V. Bulatov and E. Kaxiras}
}
@article {117,
	title = {The Peierls-Nabarro model revisited},
	journal = {Phil. Mag. Lett.},
	volume = {80},
	year = {2000},
	pages = {675},
	author = {G. Lu and N. Kioussis and V.V. Bulatov and E. Kaxiras}
}
@article {119,
	title = {A self-consistent charge density-functional based tight-binding scheme for large biomolecules},
	journal = {Phys. Stat. Sol. B},
	volume = {217},
	year = {2000},
	pages = {357},
	author = {M. Elstner and Th. Fraunenheim and E. Kaxiras and G. Seifert and S. Suhai}
}
@article {116,
	title = {Structure of III-Sb(001) growth surfaces: the role of heterodimers},
	journal = {Phys. Rev. Lett.},
	volume = {84},
	year = {2000},
	pages = {4649},
	author = {W. Barvosa-Carter and A.S. Bracker and J.C. Culbetrson and B.Z. Nosko and B.V. Shanabrook and L.J. Whitman and H. Kim and N.A. Modine and E. Kaxiras}
}
@article {0957-4484-10-2-303,
	title = {Self-organized growth of Ge quantum dots on Si(001) substrates induced by sub-monolayer C coverages},
	journal = {Nanotechnology},
	volume = {10},
	year = {1999},
	pages = {122},
	abstract = {Ge dots are grown on Si(001) substrates pre-covered with 0.05-0.1 monolayers (ML) of carbon. The C pre-deposition reduces the dot size to less than 20 nm at growth temperatures ranging from 450 to 550 ?C. In situ scanning tunnelling microscopy (STM) shows that submonolayer C-deposition locally induces c(4 ? 4) reconstruction. The reconstruction is assigned to clusters of six C atoms localized in the two topmost atomic layers in between two Si surface dimers. The non-uniform distribution of carbon together with the enhanced surface roughness give rise to the early onset of island formation at Ge coverages as low as 2.5 ML. These islands show intense photoluminescence signals at 4 K. STM and transmission electron microscopy show that the islands are irregularly shaped. No faceting is detected up to coverages of 4 ML. At 5.8 ML of Ge islands with (105) side facets and a (001) top facet are observed.},
	url = {http://stacks.iop.org/0957-4484/10/i=2/a=303},
	author = {O Leifeld and R Hartmann and E M?ller and E. Kaxiras and K Kern and D Gr?tzmacher}
}
@article {PhysRevLett.82.972,
	title = {Dimer Pairing on the C-Alloyed Si(001) Surface},
	journal = {Phys. Rev. Lett.},
	volume = {82},
	year = {1999},
	month = {Feb},
	pages = {972{\textendash}975},
	publisher = {American Physical Society},
	doi = {10.1103/PhysRevLett.82.972},
	author = {Leifeld, O. and Gr{\"u}tzmacher, D. and M{\"u}ller, B. and Kern, K. and Efthimios Kaxiras and P.C. Kelires}
}
@article {99,
	title = {Band structure calculations for semiconductors within the generalized density functionaltheory},
	journal = {Phys. Rev. B},
	volume = {59},
	year = {1999},
	pages = {5536},
	author = {I.N. Remediakis and E. Kaxiras}
}
@article {101,
	title = {Microalloying for ductility in molybdenum disilicide},
	journal = {Mat. Sci. and Engin. A},
	volume = {261},
	year = {1999},
	pages = {147},
	author = {U.V. Waghmare and V.Bulatov and E. Kaxiras and M.S. Duesbery}
}
@article {98,
	title = {Mixed finite element and atomistic formulation for complex crystals},
	journal = {Phys. Rev. B},
	volume = {59},
	year = {1999},
	pages = {235},
	author = {E. Tadmor and G.S. Smith and E. Kaxiras}
}
@article {100,
	title = {Theory of electronic and optical properties of 3c-SiC},
	journal = {J. Appl. Phys.},
	volume = {85},
	year = {1999},
	pages = {2179},
	author = {G. Theodorou and G. Tsegas and E. Kaxiras}
}
@article {102,
	title = {331 slip on (013) planes in molybdenum disilicide},
	journal = {Phil. Mag. A},
	volume = {79},
	year = {1999},
	pages = {655},
	author = {U.V. Waghmare and E. Kaxiras and V.Bulatov and M.S. Duesbery}
}
@article {106,
	title = {Concurrent coupling of length scales: methodology and application},
	journal = {Phys. Rev. B},
	volume = {60},
	year = {1999},
	pages = {2391},
	author = {J.Q. Broughton and N. Bernstein and E. Kaxiras and F.F. Abraham}
}
@article {108,
	title = {Electronic and optical properties of Si_(1-x)C_x alloys},
	journal = {Phys. Rev. B},
	volume = {60},
	year = {1999},
	pages = {11494},
	author = {G. Theodorou and G. Tsegas and P.C. Kelires and E. Kaxiras}
}
@article {103,
	title = {Linking chemical reactivity, magic numbers, and local electronic properties of clusters},
	journal = {Phys. Rev. B},
	volume = {59},
	year = {1999},
	pages = {7745},
	author = {D.R. Alfonso and S.-Y. Wu and C.S. Jayanthi and E. Kaxiras}
}
@article {105,
	title = {Metal-coated fullerenes: electronic, geometrical and vibrational properties ofC60-M62 (M=Ti and V)},
	journal = {Chem. Phys. Lett.},
	volume = {303},
	year = {1999},
	pages = {373},
	author = {M.R. Pederson and D.V. Porezag and D.C. Patton and E. Kaxiras}
}
@article {109,
	title = {Resolving discrepancies between LEED and STM through ab initio calculations: Surface structure and bonding of sulfur on Mo(110)},
	journal = {Phys. Rev. B},
	volume = {60},
	year = {1999},
	pages = {11783},
	author = {M. Chen and P.G. Clark and Jr. and T. Mueller and C.M. Friend and E. Kaxiras}
}
@article {110,
	title = {Theory of the (3 x 2) reconstruction of the GaAs(001) surface},
	journal = {Mat. Sci. and Engin. B},
	volume = {67},
	year = {1999},
	pages = {1},
	author = {N.A. Modine and E. Kaxiras}
}
@article {88,
	title = {Amorphous-crystal interface in silicon: a tight-binding simulation},
	journal = {Phys. Rev. B},
	volume = {58},
	year = {1998},
	pages = {4579},
	author = {N. Bernstein and M. J. Aziz and E. Kaxiras}
}
@article {86,
	title = {Diffusion of adsorbate atoms on the reconstructed Si(111) surface},
	journal = {Surf. Sci. Lett.},
	volume = {396},
	year = {1998},
	author = {K. Cho and E. Kaxiras}
}
@article {90,
	title = {Effects of alloying on the ductility of MoSi_2 single crystalsfrom first-principles calculations},
	journal = {Modeling and Simulation in Materials Science and Engineering},
	volume = {6},
	year = {1998},
	pages = {483},
	author = {U.V. Waghmare and E. Kaxiras and V.Bulatov and M.S. Duesbery}
}
@article {91,
	title = {Finite-temperature molecular-dynamics study of unstable stacking fault free energies in silicon},
	journal = {Phys. Rev. B},
	volume = {58},
	year = {1998},
	pages = {12555},
	author = {M. DeKoning and A. Antonelli and M.Z. Bazant and E. Kaxiras and J.F. Justo}
}
@article {87,
	title = {Interatomic potential for silicon defects and disordered phases},
	journal = {Phys. Rev. B},
	volume = {58},
	year = {1998},
	pages = {2539},
	author = {J.F. Justo and M.Z. Bazant and E. Kaxiras and V.V. Bulatov and S. Yip}
}
@article {89,
	title = {Substitutional carbon impurities in thin silicon films: equilibrium structure and properties},
	journal = {J. Vac. Sci. Technol. B},
	volume = {16},
	year = {1998},
	pages = {1687},
	author = {P.C. Kelires and E. Kaxiras}
}
@article {96,
	title = {Atomistic features of the amorphous-crystal interface in silicon},
	journal = {J. of Computer Aided Materials Design},
	volume = {5},
	year = {1998},
	pages = {55},
	author = {N. Bernstein and M. J. Aziz and E. Kaxiras}
}
@article {93,
	title = {A density functional study of clean and hydrogen-covered MoO_3(010):electronic structure and lattice relaxation},
	journal = {J. Chem. Phys.},
	volume = {109},
	year = {1998},
	pages = {6854},
	author = {M. Chen and U.V. Waghmare and C.M. Friend and E. Kaxiras}
}
@article {95,
	title = {First-principles study of static nano-scale friction betweenMoO_3 and MoS_2},
	journal = {J. of Computer Aided Materials Design},
	volume = {5},
	year = {1998},
	pages = {61},
	author = {G.S. Smith and N.A. Modine and U.V. Waghmare and E. Kaxiras}
}
@article {97,
	title = {Spanning the continuum to quantum length scales in a dynamic simulation of brittle fracture},
	journal = {Europhys. Lett.},
	volume = {44},
	year = {1998},
	pages = {783},
	author = {F.F. Abraham and J.Q. Broughton and N. Bernstein and E. Kaxiras}
}
@article {94,
	title = {Spanning the length scales in dynamic simulation},
	journal = {Computers in Physics},
	volume = {12},
	year = {1998},
	pages = {538},
	author = {F.F. Abraham and J.Q. Broughton and N. Bernstein and E. Kaxiras}
}
@article {92,
	title = {Vacancy in silicon revisited: structure and pressure effects},
	journal = {Phys. Rev. Lett.},
	volume = {81},
	year = {1998},
	pages = {2088},
	author = {A. Antonelli and E. Kaxiras and D.J. Chadi}
}
@article {78,
	title = {Adaptive coordinate real-space electronic structure calculations for atoms, molecules and solids},
	journal = {Phys. Rev. B},
	volume = {55},
	year = {1997},
	pages = {10289},
	author = {N.A. Modine and G. Zumbach and E. Kaxiras}
}
@article {79,
	title = {Energetics and equilibrium properties of thin pseudomorphic Si_(1-x)C_x(100)layers in Si},
	journal = {Phys. Rev. Lett.},
	volume = {78},
	year = {1997},
	pages = {3479},
	author = {P.C. Kelires and E. Kaxiras}
}
@article {81,
	title = {Intermittent diffusion on the Si(111)(7 x 7) surface},
	journal = {Europhys. Lett.},
	volume = {39},
	year = {1997},
	pages = {287},
	author = {K. Cho and E. Kaxiras}
}
@article {80,
	title = {Semi-discrete variational Peierls framework for dislocation core properties},
	journal = {Phys. Rev. Lett.},
	volume = {78},
	year = {1997},
	pages = {4221},
	author = {V.V. Bulatov and E. Kaxiras}
}
@article {77,
	title = {Slip energy barriers in aluminium and implications for ductile versus brittle behaviour},
	journal = {Phil. Mag. A},
	volume = {75},
	year = {1997},
	pages = {1117},
	author = {Y. Sun and E. Kaxiras}
}
@article {82,
	title = {Environment dependent interatomic potential for bulk silicon},
	journal = {Phys. Rev. B},
	volume = {56},
	year = {1997},
	pages = {8542},
	author = {M.Z. Bazant and E. Kaxiras and J.F. Justo}
}
@article {83,
	title = {Non-orthogonal tight-binding Hamiltonians for defects and interfaces in silicon},
	journal = {Phys. Rev. B},
	volume = {56},
	year = {1997},
	pages = {10488},
	author = {N. Bernstein and E. Kaxiras}
}
@article {84,
	title = {Surface reconstruction induced geometries of Si clusters},
	journal = {Phys. Rev. B},
	volume = {56},
	year = {1997},
	pages = {13455},
	author = {E. Kaxiras}
}
@article {85,
	title = {Theory of adsorption and desorption of H_2 molecules on the Si(111)-(7 x 7) surface},
	journal = {Phys. Rev. Lett.},
	volume = {79},
	year = {1997},
	pages = {5078},
	author = {K. Cho and E. Kaxiras and J.D. Joannopoulos}
}
@article {69,
	title = {Ab-initio studies of diffusion and growthphenomena on semiconductor surfaces},
	journal = {Surface Review and Letters},
	volume = {3},
	year = {1996},
	pages = {1295},
	author = {E. Kaxiras}
}
@article {70,
	title = {Adaptive coordinate, real-space electronic-structure calculations on parallel computers},
	journal = {Solid State Comm.},
	volume = {99},
	year = {1996},
	pages = {57},
	author = {G. Zumbach and N.A. Modine and E. Kaxiras}
}
@article {67,
	title = {Atomistic aspects of diffusion and growth on the Si and Ge (111) surfaces},
	journal = {Thin Solid Films},
	volume = {272},
	year = {1996},
	pages = {386},
	author = {E. Kaxiras}
}
@article {65,
	title = {Free energy of the concerted-exchange mechanism for self-diffusion in silicon},
	journal = {Phys. Rev. B},
	volume = {53},
	year = {1996},
	pages = {1310},
	author = {A. Antonelli and S. Ismail-Beigi and E. Kaxiras and K.C. Pandey}
}
@article {68,
	title = {Ledge effects on dislocation emission from a crack tip: a first-principles study for silicon},
	journal = {Phil. Mag. Lett.},
	volume = {73},
	year = {1996},
	pages = {233},
	author = {Y. Juan and Y. Sun and E. Kaxiras}
}
@article {64,
	title = {Microscopic theory of electromigration on semiconductor surfaces},
	journal = {Phys. Rev. Lett.},
	volume = {76},
	year = {1996},
	pages = {1114},
	author = {D. Kandel and E. Kaxiras}
}
@article {71,
	title = {Review of atomistic simulations of surface diffusion and growth on semiconductors},
	journal = {Computational Materials Science},
	volume = {6},
	year = {1996},
	pages = {158},
	author = {E. Kaxiras}
}
@article {66,
	title = {Variational Hilbert space truncation approach to quantum Heisenberg antiferromagnets onfrustrated clusters},
	journal = {Phys. Rev. B},
	volume = {53},
	year = {1996},
	pages = {2546},
	author = {N.A. Modine and E. Kaxiras}
}
@article {74,
	title = {Dynamic scaling in conserved systems with coupled fields:Application to surfactant mediated growth},
	journal = {Europhys. Lett.},
	volume = {36},
	year = {1996},
	pages = {129},
	author = {Barabasi,A.L. and E. Kaxiras}
}
@article {73,
	title = {Generalized stacking fault energy surfaces and idislocation properties of silicon: a first-principlestheoretical study},
	journal = {Phil. Mag. A},
	volume = {74},
	year = {1996},
	pages = {1367},
	author = {Y. Juan and E. Kaxiras}
}
@article {75,
	title = {Modeling of covalent bonding in solids by inversion of cohesive energy curves},
	journal = {Phys. Rev. Lett.},
	volume = {77},
	year = {1996},
	pages = {4370},
	author = {M.Z. Bazant and E. Kaxiras}
}
@article {76,
	title = {Simulations of structural materials},
	journal = {J. of Computer Aided Materials Design},
	volume = {3},
	year = {1996},
	pages = {30},
	author = {E. Kaxiras and J.R. Smith}
}
@article {72,
	title = {Theory of surfactant-mediated growth on semiconductor surfaces},
	journal = {Applied Surface Science},
	volume = {102},
	year = {1996},
	pages = {3},
	author = {E. Kaxiras and D. Kandel}
}
@article {56,
	title = {Atomic structure and bonding of boron-induced reconstructions on Si(001)},
	journal = {Phys. Rev. Lett.},
	volume = {74},
	year = {1995},
	pages = {403},
	author = {Y. Wang, and R.J. Hamers and E. Kaxiras}
}
@article {58,
	title = {Atomic structure of surfactant monolayers and its role in epitaxial growth},
	journal = {Mat. Sci. and Engin. B},
	volume = {30},
	year = {1995},
	pages = {175},
	author = {E. Kaxiras}
}
@article {57,
	title = {Electronic states and charge transfer mechanisms in solid molecular hydrogen},
	journal = {Computational Materials Science},
	volume = {3},
	year = {1995},
	pages = {368},
	author = {E. Kaxiras and J. Broughton}
}
@article {60,
	title = {Submonolayer island growth with adatom exchange},
	journal = {Surface Science Lett.},
	volume = {326},
	year = {1995},
	author = {A. Zangwill and E. Kaxiras}
}
@article {61,
	title = {Theoretical study of cubic structures based on fullerene carbon clusters: C28-Cand (C28)2},
	journal = {Phys. Rev. B},
	volume = {52},
	year = {1995},
	pages = {2125},
	author = {L. Zeger and Y. Juan and E. Kaxiras and A. Antonelli}
}
@article {59,
	title = {Use of the Generalized Gradient Approximation in pseudopotential calculations of solids},
	journal = {Phys. Rev. B},
	volume = {51},
	year = {1995},
	pages = {9521},
	author = {Y. Juan and E. Kaxiras and R. Gordon}
}
@article {63,
	title = {Ab initio study of hydrogen adsorption on the Si(111)-(7 x 7) surface},
	journal = {Phys. Rev. B},
	volume = {52},
	year = {1995},
	pages = {17231},
	author = {H. Lim and K. Cho and I. Park and J.D. Joannopoulos and E. Kaxiras}
}
@article {62,
	title = {Surfactant mediated crystal growth of semiconductors},
	journal = {Phys. Rev. Lett.},
	volume = {75},
	year = {1995},
	pages = {2742},
	author = {D. Kandel and E. Kaxiras}
}
@article {50,
	title = {Adatom diffusion by orchestrated exchange on semiconductor surfaces},
	journal = {Phys. Rev. Lett.},
	volume = {72},
	year = {1994},
	pages = {1714},
	author = {E. Kaxiras and J. Erlebacher}
}
@article {49,
	title = {Electronic properties of a cluster-based solid form of carbon: C28 hyperdiamond},
	journal = {Phys. Rev. B},
	volume = {49},
	year = {1994},
	pages = {8446},
	author = {E. Kaxiras and L. Zeger and A. Antonelli and Y. Juan}
}
@article {51,
	title = {Orientational order in dense molecular hydrogen: A first principles path integral Monte Carlo calculation},
	journal = {Phys. Rev. B},
	volume = {49},
	year = {1994},
	pages = {11822},
	author = {E. Kaxiras and Z. Guo}
}
@article {54,
	title = {Bonding of endohedral atoms in small carbon fullerenes},
	journal = {J. Phys. Chem.},
	volume = {98},
	year = {1994},
	pages = {7805},
	author = {K. Jackson and E. Kaxiras and M.R. Pederson}
}
@article {52,
	title = {Energetics of large lattice strains: Application to silicon},
	journal = {Phys.Rev. B},
	volume = {50},
	year = {1994},
	pages = {1535},
	author = {E. Kaxiras and L. L. Boyer}
}
@article {55,
	title = {Ideal crystal stability and pressure-induced phase transition in silicon},
	journal = {Phys. Rev. B},
	volume = {50},
	year = {1994},
	pages = {14952},
	author = {K. Mizushima and S. Yip and E. Kaxiras}
}
@article {53,
	title = {Theoretical study of passivated small fullerenes C24-X4 (X = N, P, As) and theirisoelectronic equivalents (BN)12-X4},
	journal = {Chem.Phys. Lett.},
	volume = {255},
	year = {1994},
	pages = {448},
	author = {E. Kaxiras and K. Jackson and M.R. Pederson}
}
@article {38,
	title = {Contribution of concerted exchange to the entropy of self-diffusion in Si},
	journal = {Phys. Rev. B},
	volume = {47},
	year = {1993},
	pages = {1659},
	author = {E. Kaxiras and K.C. Pandey}
}
@article {39,
	title = {Interplay of strain and chemical bonding in surfactant monolayers},
	journal = {Europhys. Lett.},
	volume = {21},
	year = {1993},
	pages = {685},
	author = {E. Kaxiras}
}
@article {41,
	title = {A new model for icosahedral carbon clusters and the structure of collapsed fullerite},
	journal = {Phys. Rev. Lett.},
	volume = {70},
	year = {1993},
	pages = {2920},
	author = {L. Zeger and E. Kaxiras}
}
@article {40,
	title = {Symmetry and stability of solitary dimer rows on Si(100)},
	journal = {Phys. Rev.Lett.},
	volume = {70},
	year = {1993},
	pages = {2589},
	author = {P. Bedrossian and E. Kaxiras}
}
@article {47,
	title = {Application of gradient corrections to density functional theory of atoms and solids},
	journal = {Phys. Rev. B},
	volume = {48},
	year = {1993},
	pages = {14944},
	author = {Y. Juan and E. Kaxiras}
}
@article {46,
	title = {Compact carbon clusters with tetrahedral bonding and icosahedral symmetry},
	journal = {Computational Materials Science},
	volume = {1},
	year = {1993},
	pages = {403},
	author = {L. Zeger and E. Kaxiras}
}
@article {48,
	title = {Electronic states of group-IV endohedral atoms in C28},
	journal = {Phys. Rev. B},
	volume = {48},
	year = {1993},
	pages = {17556},
	author = {K. Jackson and E. Kaxiras and M.R. Pederson}
}
@article {42,
	title = {Free-energies of generalized stacking faults in Si and implications for the brittle-ductile transition},
	journal = {Phys. Rev. Lett.},
	volume = {70},
	year = {1993},
	pages = {3752},
	author = {E. Kaxiras and M.S. Duesbery}
}
@article {45,
	title = {Plastic flow in Si: a first-principles study based on magic strains},
	journal = {Journal of Computer Aided Materials Design},
	volume = {1},
	year = {1993},
	pages = {55},
	author = {Y. Juan and E. Kaxiras}
}
@article {43,
	title = {The shape of small Si clusters},
	journal = {Phys. Rev. Lett.},
	volume = {71},
	year = {1993},
	pages = {727},
	author = {E. Kaxiras and K. Jackson}
}
@article {44,
	title = {Structural models for intermediate-sized Si clusters},
	journal = {Phys. D},
	volume = {26},
	year = {1993},
	pages = {346},
	author = {E. Kaxiras and K. Jackson and Z.}
}
@article {35,
	title = {Energetics of ordered structures in molecular hydrogen},
	journal = {Europhys.Lett.},
	volume = {17},
	year = {1992},
	pages = {151},
	author = {E. Kaxiras and J.Q. Broughton}
}
@article {37,
	title = {Exploring the structure of solids through magic strains: prediction of a new metallic phase of Si},
	journal = {Modeling and Simulation in Materials Science and Engineering},
	volume = {1},
	year = {1992},
	pages = {91},
	author = {E. Kaxiras and L. L. Boyer}
}
@article {36,
	title = {Theoretical modeling of heteroepitaxial growth initiation},
	journal = {Mat. Sci. and Engin. B},
	volume = {14},
	year = {1992},
	pages = {245},
	author = {E. Kaxiras and O.L. Alerhand J. Wang and J.D. Joannopoulos}
}
@article {27,
	title = {Entropy calculation beyond the harmonic approximation: application to diffusion by concerted exchange in Si},
	journal = {Phys. Rev. Lett.},
	volume = {66},
	year = {1991},
	pages = {915},
	author = {K.C. Pandey and E. Kaxiras}
}
@article {30,
	title = {Growth of GaAs overlayers on vicinal Si(100) surfaces},
	journal = {J. Vac. Sci. Technol.},
	volume = {A9},
	year = {1991},
	pages = {2423},
	author = {O.L. Alerhand J. Wang and J.D. Joannopoulos and E. Kaxiras}
}
@article {29,
	title = {Kaxiras replies (to Comment on structure of Si clusters)},
	journal = {Phys. Rev. Lett.},
	volume = {66},
	year = {1991},
	pages = {2687},
	author = {E. Kaxiras}
}
@article {31,
	title = {A new low-energy crystal structure for silicon},
	journal = {Phys. Rev. Lett.},
	volume = {67},
	year = {1991},
	pages = {715},
	author = {L. L. Boyer and E. Kaxiras and J.L. Feldman and J.Q. Broughton and M.J. Mehl}
}
@article {28,
	title = {Semiconductor surface restoration by valence mending adsorbates: application to Si(111):S and Se},
	journal = {Phys. Rev. B},
	volume = {43},
	year = {1991},
	pages = {6824},
	author = {E. Kaxiras}
}
@article {32,
	title = {Adsorption of As on stepped Si(100): resolution of the sublattice-orientation dilemma},
	journal = {Phys. Rev. B},
	volume = {44},
	year = {1991},
	pages = {6534},
	author = {O.L. Alerhand J. Wang and J.D. Joannopoulos and E. Kaxiras and R.S. Becker}
}
@article {33,
	title = {Localized adatom vibrations in Si clusters},
	journal = {Phys. Rev.B},
	volume = {44},
	year = {1991},
	pages = {8334},
	author = {J.L. Feldman and E. Kaxiras and X.-P. Li}
}
@article {34,
	title = {Onset of metallization and related transitions in solid hydrogen},
	journal = {Phys. Rev. Lett.},
	volume = {67},
	year = {1991},
	pages = {1138},
	author = {E. Kaxiras and J.Q. Broughton and R.J.Hemley}
}
@article {24,
	title = {Adsorption of boron on Si(111): physics, chemistry, and atomic-scale electronic devices},
	journal = {J. Vac. Sci. Technol.},
	volume = {A8},
	year = {1990},
	pages = {3405},
	author = {Ph. Avouris and I.-W. Lyo and F. Boszo and E. Kaxiras}
}
@article {23,
	title = {Effect of surface reconstruction on stability and reactivity of Si clusters},
	journal = {Phys. Rev. Lett.},
	volume = {64},
	year = {1990},
	pages = {551},
	author = {E. Kaxiras}
}
@article {21,
	title = {Optimized pseudopotentials},
	journal = {Phys.Rev. B},
	volume = {41},
	year = {1990},
	pages = {1227},
	author = {A.M. Rappe and K.M. Rabe and E. Kaxiras and J.D. Joanno- poulos}
}
@article {26,
	title = {Thermodynamic and kinetic aspects of GaAs growth on Si(100)},
	journal = {Superlattices and Microstructures},
	volume = {8},
	year = {1990},
	pages = {229},
	author = {E. Kaxiras and O.L. Alerhand J.D.Joannopoulos and G.W. Turner}
}
@article {PhysRevB.41.1262,
	title = {Electronic states due to surface doping: Si(111)√3{\texttimes}√3-B},
	journal = {Phys. Rev. B},
	volume = {41},
	year = {1990},
	month = {Jan},
	pages = {1262{\textendash}1265},
	publisher = {American Physical Society},
	doi = {10.1103/PhysRevB.41.1262},
	author = {Efthimios Kaxiras and K.C. Pandey and Himpsel, F. J. and R.M. Tromp}
}
@article {PhysRevB.42.7230,
	title = {Evidence for trimer reconstruction of Si(111) √3{\texttimes}√3 -Sb: Scanning tunneling microscopy and first-principles theory},
	journal = {Phys. Rev. B},
	volume = {42},
	year = {1990},
	month = {Oct},
	pages = {7230{\textendash}7233},
	publisher = {American Physical Society},
	doi = {10.1103/PhysRevB.42.7230},
	author = {M\aartensson, P. and Meyer, G. and Amer, N. M. and E. Kaxiras and K.C. Pandey}
}
@article {PhysRevB.40.2596,
	title = {Reply to {\textquoteleft}{\textquoteleft}Comment on {\textquoteleft}Ground state of the strong-coupling Hubbard Hamiltonian: A numerical diagonalization study{\textquoteright} {\textquoteright}{\textquoteright}},
	journal = {Phys. Rev. B},
	volume = {40},
	year = {1989},
	month = {Aug},
	pages = {2596{\textendash}2597},
	publisher = {American Physical Society},
	doi = {10.1103/PhysRevB.40.2596},
	author = {Efthimios Kaxiras and Manousakis, Efstratios}
}
@article {16,
	title = {Adsorption of B on Si(111): Its effect on surface electronicstates and reconstruction},
	journal = {Phys. Rev. Lett.},
	volume = {63},
	year = {1989},
	pages = {1261},
	author = {I.-W. Lyo and E. Kaxiras and Ph. Avouris}
}
@article {17,
	title = {Isolated As antisite in GaAs: possibility of the EL2 defect},
	journal = {Phys. Rev. B},
	volume = {40},
	year = {1989},
	pages = {8020},
	author = {E. Kaxiras and K.C. Pandey}
}
@article {12,
	title = {Microscopic model of heteroepitaxy of GaAs on Si(100)},
	journal = {Phys. Rev. Lett.},
	volume = {62},
	year = {1989},
	pages = {2484},
	author = {E. Kaxiras and O.L. Alerhand J.D.Joannopoulos and G.W. Turner}
}
@article {14,
	title = {Model of epitaxial growth of GaAs on Si(100) - nucleation at surface steps},
	journal = {J. Vac. Sci. Technol.},
	volume = {B7},
	year = {1989},
	pages = {695},
	author = {O.L. Alerhand E. Kaxiras and J.D. Joannopoulos and G.W. Turner}
}
@article {18,
	title = {On the possibility of two-dimensional growth of GaAs on atomically flat Si(100) surfaces},
	journal = {Surf. Sci.},
	volume = {224},
	year = {1989},
	pages = {515},
	author = {E. Kaxiras and J.D. Joannopoulos}
}
@article {19,
	title = {Scanning-tunneling microscopy and first-principles theory of the Sn/GaAs (110) surface},
	journal = {Phys. Rev. B},
	volume = {40},
	year = {1989},
	pages = {10044},
	author = {C.K. Shih and E. Kaxiras and R.M. Feenstra and K.C. Pandey}
}
@article {15,
	title = {Surfactants in epitaxial growth},
	journal = {Phys. Rev. Lett.},
	volume = {63},
	year = {1989},
	pages = {632},
	author = {M. Copel and M.C. Reuter and E. Kaxiras and R.M. Tromp}
}
@article {20,
	title = {Structural model for a covalently bonded Si45 cluster},
	journal = {Chem. Phys. Lett.},
	volume = {163},
	year = {1989},
	pages = {323},
	author = {E. Kaxiras}
}
@article {7,
	title = {Ground state of the strong-coupling Hubbard Hamiltonian: A numerical diagonalization study},
	journal = {Phys. Rev. B},
	volume = {37},
	year = {1988},
	pages = {656},
	author = {E. Kaxiras and E. Manousakis}
}
@article {8,
	title = {Hydrogenation of semiconductor surfaces: Si and Ge(111)},
	journal = {Phys. Rev. B},
	volume = {37},
	year = {1988},
	pages = {8842},
	author = {E. Kaxiras and J.D. Joannopoulos}
}
@article {10,
	title = {Energetics of defects and diffusion mechanisms in graphite},
	journal = {Phys. Rev. Lett.},
	volume = {61},
	year = {1988},
	pages = {2693},
	author = {E. Kaxiras and K.C. Pandey}
}
@article {9,
	title = {Hole dynamics in the two-dimensional strong-coupling Hubbard Hamiltonian},
	journal = {Phys. Rev. B},
	volume = {38},
	year = {1988},
	pages = {866},
	author = {E. Kaxiras and E. Manousakis}
}
@article {11,
	title = {New classical potential for accurate simulation of atomic processes in Si},
	journal = {Phys. Rev. B},
	volume = {38},
	year = {1988},
	pages = {12736},
	author = {E. Kaxiras and K.C. Pandey}
}
@article {5,
	title = {Ab-initio theory of polar semiconductor surfaces: I. Methodology and the (2 x 2)reconstructions of GaAs(111)},
	journal = {Phys. Rev. B},
	volume = {35},
	year = {1987},
	pages = {9625},
	author = {E. Kaxiras and Y. Bar-Yam and J.D. Joannopoulos and K.C. Pandey}
}
@article {6,
	title = {Ab-initio theory of polar semiconductor surfaces: II.(2 x 2) reconstructions and related transitions on GaAs(111)},
	journal = {Phys. Rev. B},
	volume = {35},
	year = {1987},
	pages = {9636},
	author = {E. Kaxiras and Y. Bar-Yam and J.D. Joannopoulos and K.C. Pandey}
}
@article {2,
	title = {(2 x 2) reconstructions of the 111 polar surfaces of GaAs},
	journal = {Phys. Rev. B},
	volume = {33},
	year = {1986},
	pages = {4406},
	author = {E. Kaxiras and Y. Bar-Yam and J.D. Joannopoulos and K.C. Pandey}
}
@article {3,
	title = {Role of chemical potentials in surface reconstruction: A new model and phase transition on GaAs(111) 2 x 2},
	journal = {Phys. Rev. Lett.},
	volume = {56},
	year = {1986},
	pages = {2819},
	author = {E. Kaxiras and K.C. Pandey and Y. Bar-Yam and J.D. Joannopoulos}
}
@article {KaxirasBarYam86,
	title = {Variable stoichiometry surface reconstructions: New models for GaAs (111)(2{\texttimes}2) and (√19{\texttimes}√19)},
	journal = {Physical Review Letters},
	volume = {57},
	year = {1986},
	month = {July},
	pages = {106{\textendash}109},
	abstract = {The $(\bar1\bar1\bar1)$ surface of GaAs exhibits three stable reconstructions. Two are $(2\times 2)$, As stabilized and Ga stabilized respectively, and the third is $(\sqrt19\times\sqrt19)$. Transitions between these structures are obtained by variation of the experimental conditions. We propose new models for all of the above reconstructions, based on ab initio total-energy calculations and experimental information regarding surface composition.},
	author = {E. Kaxiras and Y. Bar-Yam and J.D. Joannopoulos and K.C. Pandey}
}
@article {1,
	title = {Hyperon radiative decay},
	journal = {Phys. Rev. D},
	volume = {32},
	year = {1985},
	pages = {695},
	author = {E. Kaxiras and E.J. Moniz and M. Soyeur}
}
