Anomalous layer thickness dependent thermal conductivity of Td-WTe2 through first-principles calculation

2020 ◽  
Vol 384 (30) ◽  
pp. 126751
Author(s):  
Chao Wu ◽  
Chenhan Liu ◽  
Yi Tao ◽  
Yan Zhang ◽  
Yunfei Chen
Keyword(s):  
Thermal Conductivity ◽  
Layer Thickness ◽  
First Principles ◽  
First Principles Calculation

scholarly journals Pressure Effect of the Vibrational and Thermodynamic Properties of Chalcopyrite-Type Compound AgGaS2: A First-Principles Investigation

Materials ◽  
2018 ◽  
Vol 11 (12) ◽  
pp. 2370 ◽  
Author(s):  
Jianhui Yang ◽  
Qiang Fan ◽  
You Yu ◽  
Weibin Zhang
Keyword(s):  
Thermal Conductivity ◽  
Thermodynamic Properties ◽  
First Principles ◽  
Structural Parameters ◽  
Structural Phase ◽  
First Principles Calculation ◽  
Optical Phonons ◽  
Phonon Modes ◽  
Type Compound ◽  
Center Point

To explore the structural, vibrational, and thermodynamic properties of the chalcopyrite-type compound AgGaS2 under pressure, we applied hydrostatic pressure to the relaxed compound based on the first principles calculation and quasi-harmonic approximation. The structural parameters, including lattice constants and bond lengths decrease monotonically with the increasing pressure. The phonon dispersion curves under various pressures reveal the structural phase transition of chalcopyrite-type compound AgGaS2 at about 4 GPa. The intrinsic mechanism of thermal conductivity for the chalcopyrite-type compound AgGaS2 has been shown with phonon anharmonicity. The frequencies of the optical phonons at the center point Γ of the first Brillouin zone were calculated with the longitudinal optical–transverse optical (LO–TO) splitting mode. The dependence of the frequencies of the optical phonons on the pressure provides the information for the Raman spectroscopic study under high pressure. The pressure dependence of the Grüneisen parameters indicates that the instability of chalcopyrite-type compound AgGaS2 is associated with the softening of the acoustic phonon modes at around the center point Γ. The thermal conductivity for chalcopyrite-type compound AgGaS2 could be reduced by applying external pressure. The various thermodynamic properties, such as the Helmholtz free energy, entropy, and heat capacity, at different temperatures and pressures were discussed and analyzed based on the phonon properties.

Anisotropic thermal transport in Weyl semimetal TaAs: a first principles calculation

2016 ◽  
Vol 18 (25) ◽  
pp. 16709-16714 ◽  
Author(s):  
Tao Ouyang ◽  
Huaping Xiao ◽  
Chao Tang ◽  
Ming Hu ◽  
Jianxin Zhong
Keyword(s):  
Thermal Conductivity ◽  
First Principles ◽  
Thermal Transport ◽  
First Principles Calculation ◽  
Weyl Semimetal ◽  
Anisotropic Thermal Conductivity

Distinct anisotropic thermal conductivity is observed in the Weyl semimetal TaAs.

First principles calculation of thermo-mechanical properties of thoria using Quantum ESPRESSO

2016 ◽  
Vol 05 (02) ◽  
pp. 1650008 ◽  
Author(s):  
Linu Malakkal ◽  
Barbara Szpunar ◽  
Juan Carlos Zuniga ◽  
Ravi Kiran Siripurapu ◽  
Jerzy A. Szpunar
Keyword(s):  
Mechanical Properties ◽  
Thermal Conductivity ◽  
First Principles ◽  
Density Functional ◽  
Local Density ◽  
Harmonic Approximation ◽  
First Principles Calculation ◽  
Thorium Dioxide ◽  
Phonon Contribution ◽  
Quantum Espresso

In this work, we have used Quantum ESPRESSO (QE), an open source first principles code, based on density-functional theory, plane waves, and pseudopotentials, along with quasi-harmonic approximation (QHA) to calculate the thermo-mechanical properties of thorium dioxide (ThO[Formula: see text]. Using Python programming language, our group developed qe-nipy-advanced, an interface to QE, which can evaluate the structural and thermo-mechanical properties of materials. We predicted the phonon contribution to thermal conductivity ([Formula: see text] using the Slack model. We performed the calculations within local density approximation (LDA) and generalized gradient approximation (GGA) with the recently proposed version for solids (PBEsol). We employed a Monkhorst-Pack [Formula: see text] k-points mesh in reciprocal space with a plane wave cut-off energy of 150 Ry to obtain the convergence of the structure. We calculated the dynamical matrices of the lattice on a [Formula: see text] mesh. We have predicted the heat capacity, thermal expansion and the phonon contribution to thermal conductivity, as a function of temperature up to 1400[Formula: see text]K, and compared them with the previous work and known experimental results.

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