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.

scholarly journals Elastic, Mechanical, and Phonon Behavior of Orpiment Arsenic Trisulfide under Pressure

2020 ◽  
Vol 2020 ◽  
pp. 1-6
Author(s):  
Liwu Jiang ◽  
Meiling Wu ◽  
Peng Shi ◽  
Chuanhui Zhang
Keyword(s):  
Experimental Data ◽  
High Temperature ◽  
Force Field ◽  
Elastic Constants ◽  
Phonon Dispersion ◽  
Geometry Optimization ◽  
Elastic Parameters ◽  
Arsenic Trisulfide ◽  
High Temperature And Pressure ◽  
Temperature And Pressure

Arsenic trisulfide (As2S3) has been found to be an excellent glass former at high temperature and pressure. However, there is still some scarcity for the elastic and phonon behavior of the orpiment phase. By using the Dreiding force field of the geometry optimization computations, we investigated the elastic constants, mechanical moduli, and the phonon dispersion of orpiment As2S3 under the pressure from 0 to 5 GPa. Some results of the elastic parameters of orpiment-As2S3 at 0 GPa are consistent with the experimental data. The phonon dispersions for orpiment As2S3 under pressure are also reasonable with previous calculations.

Elastic constants and anisotropic pair correlations in solid hydrogen and deuterium

1979 ◽  
Vol 57 (2) ◽  
pp. 136-146 ◽  
Author(s):  
S. Luryi ◽  
J. Van Kranendonk
Keyword(s):  
Elastic Constants ◽  
Phonon Dispersion ◽  
Debye Model ◽  
Elasticity Tensor ◽  
Pair Correlations ◽  
Nearest Neighbours ◽  
Einstein Model ◽  
The One ◽  
Central Forces ◽  
Phonon Dispersion Relations

The anisotropic displacement–displacement correlation function for the two types of pairs of nearest neighbours in solid hep hydrogen and deuterium is studied. Two mechanisms contributing to the deviation of the pair distribution function from axial symmetry around the pair axis are identified. The one is due to the anisotropy of the phonon dispersion relations and is treated in a generalized Debye model parameterized in terms of the elastic constants. The elasticity tensor is decomposed into rotationally irreducible parts, and certain new relations between the elastic constants of hep crystals with central forces are derived. The other mechanism arises from the immediate, anisotropic environment of a pair and is treated using a generalized Einstein model. The relevance of these results for the interpretation of the microwave spectrum of pairs of orthohydrogen molecules in parahydrogen is also discussed.

scholarly journals Emergence of Superconductivity in LaOFeAs: Electronic Structure and Lattice Dynamics

2010 ◽  
Vol 3 (1) ◽  
pp. 1 ◽  
Author(s):  
M. Aftabuzzaman ◽  
A.K.M. A. Islam ◽  
S. H. Naqib
Keyword(s):  
Band Structure ◽  
Density Of States ◽  
Elastic Constants ◽  
Phonon Dispersion ◽  
Electronic Band Structure ◽  
Parent Compound ◽  
Electronic Density ◽  
Electronic Band ◽  
High Tc ◽  
Carrier Doping

In view of continuing interest in the parent compound of the recently discovered superconducting iron-oxypnictide (LaO1-xFxFeAs) we present fresh results and analyses of ab-initio calculations of the electronic band structure, lattice dynamical properties, and elastic constants assuming it to be insulating as well as metallic. The total and partial electronic density of states (EDOS) of the undoped LaOFeAs in both states are extracted from the electronic band structure. The phonon dispersion and the phonon density of states (PDOS) are also studied. Possible implications of the band structure, EDOS, and PDOS of LaOFeAs on the eventual appearance of high-Tc superconductivity upon carrier doping are discussed. Our findings reveal that phonons are unlikely to mediate Cooper pairing in RE-OFeAs. In addition, the values of various independent elastic constants of the compound assuming both insulating and metallic states are estimated and discussed. Keywords: LaOFeAs; Electronic band structure; Phonon spectrum; Elastic constants; Superconductor.© 2011 JSR Publications. ISSN: 2070-0237 (Print); 2070-0245 (Online). All rights reserved.doi:10.3329/jsr.v3i1.6211                J. Sci. Res. 3 (1), 1-11 (2011)

Computational Study of Ru2TiZ (Z = Si, Ge, Sn) for Structural, Mechanical and Vibrational Properties

2019 ◽  
Vol 74 (6) ◽  
pp. 545-550
Author(s):  
Aneeza Iftikhar ◽  
A. Afaq ◽  
Iftikhar Ahmad ◽  
Abu Bakar ◽  
H. Bushra Munir ◽  
...  
Keyword(s):  
Elastic Constants ◽  
Phonon Dispersion ◽  
Computational Study ◽  
Heusler Alloys ◽  
Vibrational Properties ◽  
Mechanical Parameters ◽  
Phonon Modes ◽  
Lattice Constants ◽  
The Stability ◽  
Experimental Values

AbstractThe structural, mechanical and vibrational properties of Ru2TiZ (Z = Si, Ge, Sn) Full Heusler Alloys (FHAs) are computed using PBE-GGA as an exchange-correlation functional in Kohn–Sham equations. The calculated lattice constants of these alloys in L21 phase deviate from experimental values upto 0.85 % which shows a good agreement between the model and the experiments. These lattice constants are then used to compute the second order elastic constants C11, C12 and C44 with Wien2k-code. Elastic moduli and mechanical parameters are also calculated by these three independent elastic constants. Mechanical parameters Pugh’s and Poisson’s ratio indicate non-brittle nature of these alloys. Furthermore, the Debye temperature where the collective vibrations shift to an independent thermal vibration, longitudinal and transverse sound velocities, melting temperatures, and thermal conductivities are also obtained to investigate the phonon modes of oscillation. These phonon modes confirm the stability of these alloys as there exists no imaginary phonon frequency in the phonon-dispersion curves.

Elastic Constants and Phonon Dispersion Curves for Solid Argon near 0 °K

1970 ◽  
Vol 2 (10) ◽  
pp. 4176-4179 ◽  
Author(s):  
J. A. Barker ◽  
M. L. Klein ◽  
M. V. Bobetic
Keyword(s):  
Elastic Constants ◽  
Phonon Dispersion ◽  
Dispersion Curves ◽  
Phonon Dispersion Curves ◽  
Solid Argon
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