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Full-Text Articles in Physics
Disorder By Design: A Data-Driven Approach To Amorphous Semiconductors Without Total-Energy Functionals, Dil K. Limbu, Stephen R. Elliott, Raymond Atta-Fynn, Parthapratim Biswas
Disorder By Design: A Data-Driven Approach To Amorphous Semiconductors Without Total-Energy Functionals, Dil K. Limbu, Stephen R. Elliott, Raymond Atta-Fynn, Parthapratim Biswas
Faculty Publications
X-ray diffraction, Amorphous silicon, Multi-objective optimization, Monte Carlo methods. This paper addresses a difficult inverse problem that involves the reconstruction of a three-dimensional model of tetrahedral amorphous semiconductors via inversion of diffraction data. By posing the material-structure determination as a multiobjective optimization program, it has been shown that the problem can be solved accurately using a few structural constraints, but no total-energy functionals/forces, which describe the local chemistry of amorphous networks. The approach yields highly realistic models of amorphous silicon, with no or only a few coordination defects (≤1%), a narrow bond-angle distribution of width 9–11.5°, and an electronic gap …
Semiconductor Color-Center Structure And Excitation Spectra: Equation-Of-Motion Coupled-Cluster Description Of Vacancy And Transition-Metal Defect Photoluminescence, Jesse J. Lutz, Xiaofeng F. Duan, Larry W. Burggraf
Semiconductor Color-Center Structure And Excitation Spectra: Equation-Of-Motion Coupled-Cluster Description Of Vacancy And Transition-Metal Defect Photoluminescence, Jesse J. Lutz, Xiaofeng F. Duan, Larry W. Burggraf
Faculty Publications
Valence excitation spectra are computed for deep-center silicon-vacancy defects in 3C, 4H, and 6H silicon carbide (SiC), and comparisons are made with literature photoluminescence measurements. Optimizations of nuclear geometries surrounding the defect centers are performed within a Gaussian basis-set framework using many-body perturbation theory or density functional theory (DFT) methods, with computational expenses minimized by a QM/MM technique called SIMOMM. Vertical excitation energies are subsequently obtained by applying excitation-energy, electron-attached, and ionized equation-of-motion coupled-cluster (EOMCC) methods, where appropriate, as well as time-dependent (TD) DFT, to small models including only a few atoms adjacent to the defect center. We consider the …
Density Functional Theory Study On The Electronic Structure Of N- And P-Type Doped Srtio3 At Anodic Solid Oxide Fuel Cell Conditions, S. Suthirakun, Salai Cheettu Ammal, G. Xiao, Fanglin Chen, Hans-Conrad Zur Loye, Andreas Heyden
Density Functional Theory Study On The Electronic Structure Of N- And P-Type Doped Srtio3 At Anodic Solid Oxide Fuel Cell Conditions, S. Suthirakun, Salai Cheettu Ammal, G. Xiao, Fanglin Chen, Hans-Conrad Zur Loye, Andreas Heyden
Faculty Publications
The electronic conductivity and thermodynamic stability of mixed n-type and p-type doped SrTiO3 have been investigated at anodic solid oxide fuel cell (SOFC) conditions using density functional theory (DFT) calculations. In particular, constrained ab initio thermodynamic calculations have been performed to evaluate the phase stability and reducibility of various Nb- and Ga-doped SrTiO3 at synthesized and anodic SOFC conditions. The density of states (DOS) of these materials was analyzed to study the effects of n- and p-doping on the electronic conductivity. In agreement with experimental observations, we find that the transformation from 20% Nb-doped Sr-deficient SrTiO3 to a non-Sr-deficient phase …
First-Principles Elastic Constants And Electronic Structure Of Α-Pt2si And Ptsi, Gus L. W. Hart, O. Beckstein, J. E. Klepeis, O. Pankratov
First-Principles Elastic Constants And Electronic Structure Of Α-Pt2si And Ptsi, Gus L. W. Hart, O. Beckstein, J. E. Klepeis, O. Pankratov
Faculty Publications
We have carried out a first-principles study of the elastic properties and electronic structure for two room-temperature stable Pt silicide phases, tetragonal α-Pt2Si, and orthorhomic PtSi. We have calculated all of the equilibrium structural parameters for both phases; the a and c lattice constants for α-Pt2Si and the a, b, and c lattice constants and four internal structural parameters for PtSi. These results agree closely with experimental data. We have also calculated the zero-pressure elastic constants, confirming prior results for pure Pt and Si and predicting values for the six (nine) independent, nonzero elastic constants of α-Pt2Si (PtSi). These calculations …
Electronic Structure Of Bas And Boride Iii-V Alloys, Gus L. W. Hart, Alex Zunger
Electronic Structure Of Bas And Boride Iii-V Alloys, Gus L. W. Hart, Alex Zunger
Faculty Publications
Boron arsenide, the typically ignored member of the Group-III–V arsenide series BAs-AlAs-GaAs-InAs is found to resemble silicon electronically: its Γ conduction-band minimum is p-like (Γ15), not s-like (Γ1c), it has an X1c-like indirect band gap, and its bond charge is distributed almost equally on the two atoms in the unit cell, exhibiting nearly perfect covalency. The reasons for these are tracked down to the anomalously low atomic p orbital energy in the boron and to the unusually strong s–s repulsion in BAs relative to most other Group-III–V compounds. We find unexpected valence-band offsets of BAs with respect to GaAs and …
Electronic Structure Of Cu1-Xnixrh2s4 And Curh2se4: Band-Structure Calculations, X-Ray Photoemission, And Fluorescence Measurements, Gus L. W. Hart, W. E. Pickett, E. Z. Kurmaev, M. Neumann, D. Hartmann, A. Moewes, D. L. Ederer, R. Endoh, K. Taniguchi, S. Nagata
Electronic Structure Of Cu1-Xnixrh2s4 And Curh2se4: Band-Structure Calculations, X-Ray Photoemission, And Fluorescence Measurements, Gus L. W. Hart, W. E. Pickett, E. Z. Kurmaev, M. Neumann, D. Hartmann, A. Moewes, D. L. Ederer, R. Endoh, K. Taniguchi, S. Nagata
Faculty Publications
The electronic structure of spinel-type Cu1-xNixRh2S4 (x=0.0, 0.1, 0.3, 0.5, 1.0) and CuRh2Se4 compounds has been studied by means of x-ray photoelectron (SPS) and fluorescent spectroscopy. Cu L3, Ni L3, S L2,3, and Se M2,3 x-ray emission spectra (XES) were measured near thresholds at Beamline 8.0 of the Lawrence Berkeley Laboratory's Advanced Light Source. XES measurements of the constituent atoms of these compounds, reduced to the same binding energy scale, are found to be in excellent agreement with XPS valence bands. The calculated XES spectra which include dipole matrix elements show that the partial density of states reproduce experimental spectra …
Model Of Electron Correlation In Solids, Everett G. Larson, Walter R. Thorson
Model Of Electron Correlation In Solids, Everett G. Larson, Walter R. Thorson
Faculty Publications
The usual Hartree-Fock model (energy-band theory) does not always give an adequate description of electronic structure in a solid, because it ignores the effects of electron correlation. It was shown first by Wigner that such a situation always develops in an electron ''gas'' at sufficiently low density; a solid structure described by ''resonance'' of Heitler-London pair bonds between electrons localized on neighboring atoms is then a good model of the system.The transition from a Bloch-type state to such a highly correlated state as a function of electron density (lattice parameter) is a problem of considerable interest for the theory of …