Publications by Year: 2011

2011
Mao Y, Wang WL, Wei D, Kaxiras E, Sodroski JG. Graphene Structures at an ExtremeDegree of Buckling. ACSNano. 2011;5 :1395.
Ren J, Meng S, Wang Y-L, Ma X-C, Xue Q-K, Kaxiras E. Properties of copper (fluoro-)phthalocyanine layers depositedon epitaxial graphene. J. Chem. Phys. 2011;134 :194706.
Baker TA, Xu B, Jensen SC, andEfthimios Kaxiras CMF. Role of defects in propene adsorption and reaction on a partiallyO-covered Au(111) surface. Catal. Sci. Technol. 2011;1 :1166.
Haubrich J, Kaxiras E, Friend CM. The Role of Surface and Subsurface Point Defects for Chemical ModelStudies on TiO2: A First-Principles Theoretical Study of FormaldehydeBonding on Rutile TiO2(110). Chem. Eur. J. 2011;17 :4496.
Li H, Knaup JM, Kaxiras E, Vlassak JJ. Stiffening of organosilicate glasses by organic cross-linking. Acta Mater. 2011;59 :44.
Lin M-W, Ling C, Agapito LA, Kioussis N, Zhang Y, Cheng MM-C, Wang WL, Kaxiras E, Zhixian Zhou1. Approaching the intrinsic band gap in suspended high-mobility graphene nanoribbons. PHYSICAL REVIEW B. 2011;84 :125411.
Meng S, Kaxiras E, Nazeeruddin MK, Gratzel M. Design of Dye Acceptors for Photovoltaics from First-PrinciplesCalculations. J. Phys. Chem. C. 2011;115 :9276.
Heiss M, Conesa-Boj S, Ren J, Tseng H-H, Gali A, Rudolph A, Uccelli E, Peiro F, Morante JR, Schuh D, et al. Direct correlation of crystal structure and optical properties in wurtzite/zinc-blendeGaAs nanowire heterostructures. PHYSICAL REVIEW B. 2011;83 :045303.
Gali JA, Kaxiras E, Zimanyi GT, Meng S. Effect of symmetry breaking on the optical absorption of semiconductor nanoparticles. PHYSICAL REVIEW B. 2011;84 :035325.
Melchionna S, Kaxiras E, Bernaschi M, Succi S. Endothelial shear stress from large-scale blood flow simulations. Phil. Trans. R. Soc. A. 2011;369 :2354.
Knaup JM, Li H, Vlassak JJ, Kaxiras E. Influence of CH2 content and network defects on the elastic properties of organosilicate glasses. PHYSICAL REVIEW B. 2011;83 :054204.
Zhao K, Wang WL, Gregoire J, Pharr M, Suo Z, Vlassak JJ, Kaxiras E. Lithium-Assisted Plastic Deformation of Silicon Electrodes inLithium-Ion Batteries: A First-Principles Theoretical Study. Nano Lett. 2011;11 :2962.
Kuhne TD, Pascal TA, Kaxiras E, Jung Y. New Insights into the Structure of the Vapor/WaterInterface from Large-Scale First-Principles Simulations. J. Phys. Chem. Lett. 2011;2 :105.
Maze JR, Gali A, Togan E, Chu Y, Trifonov A, Kaxiras E, Lukin MD. Properties of nitrogen-vacancy centers in diamond:the group theoretic approach. New Journal of Physics. 2011;13 :025025.
Xu B, Haubrich J, Baker TA, Kaxiras E, Friend CM. Theoretical Study of O-Assisted Selective Coupling of Methanol onAu(111). J. Phys. Chem. C. 2011;115 :3703.
Katono M, Bessho T, Meng S, Humphry-Baker R, Rothenberger G, Zakeeruddin SM, Kaxiras E, Gratzel M. D-π-A Dye System Containing Cyano-Benzoic Acid as Anchoring Group for Dye-Sensitized Solar Cells. Langmuir. 2011;27 (23) :14248–14252.
Meng S, Kaxiras E, Nazeeruddin MK, Graetzel M. Design of Dye Acceptors for Photovoltaics from First-Principles Calculations. Journal of Physical Chemistry C. 2011;115 :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.

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Heiss M, Conesa-Boj S, Ren J, Tseng H-H, Gali A, Rudolph A, Uccelli E, Peiro F, Morante JR, Schuh D, et al. Direct correlation of crystal structure and optical properties in wurtzite/zinc-blende GaAs nanowire heterostructures. Physical Review B. 2011;83 :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.

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Katono M, Bessho T, Meng S, Humphry-Baker R, Rothenberger G, Zakeeruddin SM, Kaxiras E, Graetzel M. D-π-A Dye System Containing Cyano-Benzoic Acid as Anchoring Group for Dye-Sensitized Solar Cells. Langmuir. 2011;27 :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

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Melchionna S, Kaxiras E, Bernaschi M, Succi S. Endothelial shear stress from large-scale blood flow simulations. Philosophical Transactions of the Royal Society A. 2011;369 :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.

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