Density-functional calculation of static and dynamic properties of GaAs

1981 ◽  
Vol 24 (4) ◽  
pp. 2311-2314 ◽  
Author(s):  
K. Kunc ◽  
Richard M. Martin
Keyword(s):  
Density Functional ◽  
Dynamic Properties ◽  
Density Functional Calculation

Anisotropic gap of superconductingCaC6: A first-principles density functional calculation

2007 ◽  
Vol 75 (2) ◽  
Author(s):  
A. Sanna ◽  
G. Profeta ◽  
A. Floris ◽  
A. Marini ◽  
E. K. U. Gross ◽  
...  
Keyword(s):  
First Principles ◽  
Density Functional ◽  
Density Functional Calculation

scholarly journals Theory of the Thermal Stability of Silicon Vacancies and Interstitials in 4H–SiC

Crystals ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 167
Author(s):  
José Coutinho
Keyword(s):  
Thermal Stability ◽  
Fermi Level ◽  
Density Functional ◽  
Dynamic Properties ◽  
Type Material ◽  
Temperature Threshold ◽  
Effect Analysis ◽  
Mobile Species ◽  
Two Stages ◽  
Thermal Stability Of

This paper presents a theoretical study of the electronic and dynamic properties of silicon vacancies and self-interstitials in 4H–SiC using hybrid density functional methods. Several pending issues, mostly related to the thermal stability of this defect, are addressed. The silicon site vacancy and the carbon-related antisite-vacancy (CAV) pair are interpreted as a unique and bistable defect. It possesses a metastable negative-U neutral state, which “disproportionates” into VSi+ or VSi−, depending on the location of the Fermi level. The vacancy introduces a (−/+) transition, calculated at Ec−1.25 eV, which determines a temperature threshold for the annealing of VSi into CAV in n-type material due to a Fermi level crossing effect. Analysis of a configuration coordinate diagram allows us to conclude that VSi anneals out in two stages—at low temperatures (T≲600 °C) via capture of a mobile species (e.g., self-interstitials) and at higher temperatures (T≳1200 °C) via dissociation into VC and CSi defects. The Si interstitial (Sii) is also a negative-U defect, with metastable q=+1 and q=+3 states. These are the only paramagnetic states of the defect, and maybe that explains why it escaped detection, even in p-type material where the migration barriers are at least 2.7 eV high.

Study of thermo-elastic and lattice dynamics properties of half-Heusler compounds XMgAl (X = Li, Na) by computational investigations

2019 ◽  
Vol 33 (08) ◽  
pp. 1950093 ◽  
Author(s):  
A. Afaq ◽  
Abu Bakar ◽  
M. Rizwan ◽  
M. Aftab Fareed ◽  
H. Bushra Munir ◽  
...  
Keyword(s):  
Debye Temperature ◽  
Elastic Constants ◽  
Density Functional ◽  
Phonon Dispersion ◽  
Dynamic Properties ◽  
Mechanical Parameters ◽  
Heusler Compounds ◽  
Generalized Gradient ◽  
Text Type ◽  
Quantum Espresso

In this study, thermo-elastic and lattice dynamic properties of XMgAl (X = Li, Na) half-Heusler compounds are investigated using density functional theory implemented in WIEN2k and Quantum ESPRESSO codes. Generalized gradient approximation (GGA) as an exchange correlation function has been used in Kohn–Sham equations. Firstly, the structure of these Heusler compounds is optimized and then these optimized parameters are used to find three elastic constants [Formula: see text], [Formula: see text] and [Formula: see text] for [Formula: see text] type structures. Three elastic constants are then used to determine different elastic moduli like bulk modulus, shear modulus, Young’s modulus and other mechanical parameters like Pugh’s ratio, Poisson’s ratio, anisotropic ratio, sound velocities, Debye temperature and melting temperature. On behalf of these mechanical parameters, the brittle/ductile nature and isotropic/anisotropic behavior of the materials has been studied. Different regions of vibrational modes in the materials are also discussed on behalf of Debye temperature calculations. The vibrational properties of the half-Heusler compounds are computed using Martins–Troullier pseudo potentials implemented in Quantum ESPRESSO. The phonon dispersion curves and phonon density of states in first Brillion zone are obtained and discussed. Reststrahlen band of LiMgAl is found greater than NaMgAl.

Band structure and optical properties of SbSeI: density-functional calculation

2007 ◽  
Vol 244 (10) ◽  
pp. 3673-3683 ◽  
Author(s):  
Harun Akkus ◽  
Ali Kazempour ◽  
Hadi Akbarzadeh ◽  
Amirullah M. Mamedov
Keyword(s):  
Optical Properties ◽  
Band Structure ◽  
Density Functional ◽  
Density Functional Calculation

Simple spin correction of unrestricted density-functional calculation

1996 ◽  
Vol 53 (6) ◽  
pp. 3946-3952 ◽  
Author(s):  
Alexander A. Ovchinnikov ◽  
Jan K. Labanowski
Keyword(s):  
Density Functional ◽  
Density Functional Calculation
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