Search query: Ab initio calculations of hardness, elastic, thermodynamic and electronic properties of metal nitrides (XN2; , Pt) under high-pressure

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abstract: We have performed first principles calculations within density functional theory (DFT) to investigate the hardness, elastic, thermodynamic and electronic properties of metal nitrides compounds (XN2; X Pd, Pt) in pyrite structure, under high hydrostatic pressure. The calculated structural properties match with those previously reported experimental and theoretical data. The Vickers hardness of PdN2 and PtN2 compounds were calculated in 7.5 and 27.7 GPa, respectively. We also calculated the electronic properties of both compounds. The calculated electronic band structure of PtN2 at either 0 GPa or 153 GPa reveals that this compound is an indirect semiconductor. The top of the valence band is located at M point, whereas the bottom of the conduction band at L point at zero pressure or at S point at 153 GPa. In the case of PdN2, it was found a conductor semiconductor transition at 104 GPa.
author_names: Jose Humberto Camacho-Garcia

J C Moreno-Hernandez

Ma L Ruiz-Peralta

Alejandro Bautista-Hernandez

Alejandro Escobedo-Morales
title: Ab initio calculations of hardness, elastic, thermodynamic and electronic properties of metal nitrides (XN2; X Pd, Pt) under high pressure
year: 2019

abstract: Co2Zr and Co2Ti are both cubic crystals with a Cu2Mg type structure. The elastic, thermodynamic and electronic properties of the intermetallic compounds Co2Zr and Co2Ti are investigated by using ab initio plane wave pseudopotential density functional theory (PWPDFT) and generalized gradient approximation (GGA) under high temperature and pressure. The partially calculated results are consistent with the available experimental data. The elastic properties of Co2Zr and Co2Ti under high pressure were first studied by first principles calculations. The results indicate that the elastic constants, elastic modulus and Poisson's ratio are functions of pressure, indicating that the effect of pressure on the ductility and anisotropy is significant. The thermodynamic properties are also calculated by the quasi harmonic Debye model. In the range of 0~100 GPa pressure and 0~1500 K temperature, the Debye temperature Th, the heat capacity CV and the thermal expansion a vary with pressure and temperature. Co2Ti has a higher Debye temperature than Co2Zr under the same pressure. Decreasing temperature and increasing pressure have the same effects on CV and a. The electron density difference and density of states of Co2Zr and Co2Ti are finally investigated. The results show that both Co2Zr and Co2Ti are typically metal crystals but Co2Zr has greater covalence than Co2Ti.
author_names: Mi-An Xue

Xiaoli Yuan

Cheng Zhong

Peng Wan
title: First Principles Calculations on Elastic, Thermodynamic and Electronic Properties of Co2Zr and Co2Ti at High Temperature and Pressure
year: 2020

abstract: Abstract First principles calculations are performed to investigate the structural, elastic, and electronic properties of the Mo3.46B12 under pressure based on the generalized gradient approximation (GGA) proposed by Perdew Wang (PW91) The initial results show that the optimized lattice parameters at a pressure of zero GPa are in good agreement with the experimental and other theoretical results. The effect of high pressure on the crystal structure reveals that the compression along the c axis is stronger than along the a axis. We find that the elastic constants, elastic modulus, hardness, and Debye temperature (thD) increase and the Gruneisen parameter (g) decreases due to stiffening of the crystal structure under pressure. Consequently, the structure is mechanically stable, brittle, and elastically anisotropic. Finally, the density of states at Fermi level N(EF) decreases under pressure due to decreasing of the B 2p states. Graphical abstract
author_names: J Leon-Flores

M Romero

Julian Rosas

R Escamilla
title: Ab initio study of structural, elastic, and electronic properties of Mo3.46B12 under high pressure
venue: The European Physical Journal B
year: 2019

abstract: The structural, electronic, magnetic and mechanical properties of the full Heusler Mn2CoGa have been systematically investigated by first principles calculations based on density functional theory. The determined ground state structural configuration and equilibrium lattice constant are consistent with previous theoretical and experimental studies. Mn2CoGa shows metallic nature since the band structure overlaps with the Fermi energy level in both spin directions. The total magnetic moment is mainly from the two transition metal atoms and it follows the Slater Pauling rule, MTotal ZTotal 24. Several mechanical parameters at the equilibrium lattice are calculated and provided. Mn2CoGa behaves in a brittle manner from the computed elastic moduli, whereas Mn2CoGa shows very strong anisotropy, which is revealed by the calculated direction dependent Young's modulus and shear modulus. In the last section, we further examine the thermodynamic properties of Mn2CoGa by employing the quasi harmonic Debye model and study the variation of its cell volume, thermal expansion coefficient, heat capacity, Gruneisen constant and Debye temperature under a pressure range from 0 to 5 GPa and temperature range from 0 to 1000 K. This study provides a detailed theoretical analysis of the full Heusler compound Mn2CoGa and can give helpful guidance for further relative research.
author_names: Liyu Hao

Rabah Khenata

Xiaotian Wang

Tie Yang
title: Ab Initio Study of the Structural, Electronic, Magnetic, Mechanical and Thermodynamic Properties of Full Heusler Mn2CoGa
venue: Journal of Electronic Materials
year: 2019

abstract: Ab initio calculations were used to study the properties of a series of hexagonal (Fe2N like) subcarbides M2C, where M Tc, Ru, Rh, Pd, Re, Os, Ir, and Pt, and to calculate their equilibrium structural parameters, electronic properties, phase stability, elastic constants, compression modulus, shear modulus, Young's modulus, compressibility, Pugh's indicator, Poisson ratio, elastic anisotropy indices, and also hardness, Debye temperature, sound velocity, and low temperature heat capacity. It is found based on these results that all the subcarbides are mechanically stable; however, their formation energies Eform are positive with respect to a mixture of d metal and graphite. In addition, the calculation of the phonon spectra of these subcarbides shows the existence of negative modes, which indicates their dynamical instability. Thus, a successful synthesis of these subcarbides at normal conditions is highly improbable.
author_names: D V Suetin

I R Shein
title: Electronic Structure, Mechanical and Dynamical Stability of Hexagonal Subcarbides M2C (M Tc, Ru, Rh, Pd, Re, Os, Ir, and Pt) Ab Initio Calculations
year: 2018

abstract: Abstract The mechanical, electronic and thermodynamic properties of MTe 2 (M Ni, Pd and Pt) under high pressure were investigated via the first principles calculations. According to our calculations of these trigonal crystals (space group of P3M1 No: 164) we found that all of them are fulfilled by the mechanical stability criteria under 31 GPa (for NiTe 2 37 GPa (for PdTe 2 and 73 GPa (for PtTe 2 The study on their structures revealed the elastic anisotropy of these isostructural compounds. Electronic structure calculations show that MTe 2 are semi metal. On the basis of the quasi harmonic Debye model, we also researches their thermodynamic properties.
author_names: Jinqiao Lei

Ke Ping Liu

Shan Huang

Xiao-Chun Mao

Bao-Sen Hou

Jiao Tan

Xiaolin Zhou
title: Theoretical study of isostructural compounds MTe 2 (M Ni, Pd and Pt) on structure and thermodynamic properties under high pressures
year: 2017

abstract: The structural, electronic, elastic and thermodynamic properties of Curium Monopnictides CmX (X N, P, As, Sb and Bi) are investigated using first principles calculations based on the density functional theory (DFT) and full potential linearized augmented plane wave (FP LAPW) method under ambient condition and high pressure. The exchange correlation term is treated using two approximations spin polarized local density approximation (LSDA) and spin polarized generalized gradient approximation generalized (GGA) The structural parameters such as the equilibrium lattice parameters, bulk modulus and the total energies are calculated in two phases: namely NaCl (B1) and CsCl (B2) The obtained results are compared with the previous theoretical and experimental results. A structural phase transition from B1 phase to B2 phase for Curium pnictides has been obtained. The highest transition pressure is 122 GPa for CmN and the lowest one is 10.0 GPa for CmBi compound. The electronic properties show that these materials exhibit half metallic behavior in both phases. The magnetic moment is found to be around 7.0 mB. The mechanical properties of CmX (X N, P, As, Sb and Bi) are predicted from the calculated elastic constants. Our calculated results are in good agreement with the theoretical results in literature. The effect of pressure and temperature on the thermodynamic properties like the cell volume, bulk modulus and the specific heats C and CP, the entropy S and the Gruneisen parameter g have been foreseen at expanded pressure and temperature ranges.
author_names: Hakim Baaziz

Dj Guendouz

Z Charifi

Salih Akbudak

G Ugur

S Ugur

Khaouther Boudiaf
title: Investigation of the structural, electronic, elastic and thermodynamic properties of Curium Monopnictides: An ab initio study
year: 2017

abstract: Abstract The structural, electronic, elastic and vibrational properties of boron nitride (BN) were analyzed using ab initio computational methods based on density functional theory. The exchange correlation energy functional was evaluated using the local density approximation (LDA) under pressure. BN crystallizes in hexagonal structure (h BN) with symmetry P 6 3 mmc The structural transform was obtained at the BN from h BN transformed into wurtzite (w BN) with symmetry P 6 3 mc at 12.5 GPa. During this phase transformation, intermediate states with space group P 3 m 1 and P3m1were observed. Besides, the electronic properties for the obtained stable phases of BN were calculated. Both structures have a semiconductor character with a direct band gap. We also made elastic and phonon calculations to understand the mechanical and dynamically stability of the obtained phases of BN. BN is stable in both phases. As a result of the literature searches, the obtained intermediate states were first predicted in this study. Thus, we believe that this study will guide the experimental studies to be conducted.
author_names: Cihan Kurkcu

Cagatay Yamcicier
title: Structural, electronic, elastic and vibrational properties of two dimensional graphene like BN under high pressure
year: 2019

abstract: Abstract The lattice parameters, cell volume, elastic constants, bulk modulus, shear modulus, Young's modulus and Poisson's ratio are calculated at zero pressure, and their values are in excellent agreement with the available data, for TiN, Ti2N and Ti3N2. By using the elastic stability criteria, it is shown that the three structures are all stable. The brittle/ductile behaviors are assessed in the pressures from 0 GPa to 50 GPa. Our calculations present that the performances for TiN, Ti2N and Ti3N2 become from brittle to ductile with pressure rise. The Debye temperature rises as pressure increase. With increasing N content, the enhancement of covalent interactions and decline of metallicity lead to the increase of the micro hardness. Their constant volume heat capacities increase rapidly in the lower temperature, at a given pressure. At higher temperature, the heat capacities are close to the Dulong Petit limit, and the heat capacities of TiN and Ti2N are larger than that of c BN. The thermal expansion coefficients of titanium nitrides are slightly larger than that of c BN. The band structure and the total Density of States (DOS) are calculated at 0 GPa and 50 GPa. The results show that TiN and Ti2N present metallic character. Ti3N2 present semiconducting character. The band structures have some discrepancies between 0 GPa and 50 GPa. The extent of energy dispersion increases slightly at 50 GPa, which means that the itinerant character of electrons becomes stronger at 50 GPa. The main bonding peaks of TiN, Ti2N and Ti3N2 locate in the range from 10 to 10 eV, which originate from the contribution of valance electron numbers of Ti s, Ti p, Ti d, N s and N p orbits. We can also find that the pressure makes that the total DOS decrease at the Fermi level for Ti2N. The bonding behavior of N Ti compounds is a combination of covalent and ionic nature. As N content increases, valence band broadens, valence electron concentration increases, and covalent interactions become stronger. This is reflected in shortening of Ti N bonds.
author_names: Ruike Yang

Chuanshuai Zhu

Qun Wei

Zhengliang Du
title: Investigations on structural, elastic, thermodynamic and electronic properties of TiN, Ti 2 N and Ti 3 N 2 under high pressure by first principles
year: 2016

abstract: The structural, elastic, thermodynamic and electronic properties of nonmetallic metal FeCrAs are studied within density function perturbation theory. The thermodynamic properties of FeCrAs were deduced based on phonon frequencies within the framework of the quasiharmonic approximation. The calculated elastic modulus under various pressures indicates that FeCrAs is mechanically stable under pressure. The pressure dependence of bulk and shear modulus, transverse and longitudinal sound velocities V (i.e. VS and VL) elastic Debye temperature ThE of FeCrAs have also been investigated. The calculated values of B/G indicate that FeCrAs presents high ductility under pressure. However, it is interesting that the value of B/G reaches a maximum under 40 GPa and almost remains unchanged when the pressure is above 70 GPa. The calculations show that the heat capacity CV of this material is close to the Dulong Petit limit 3R (about 224.61 J mol 1 K 1) at high temperature regime. The analysis of electronic properties nd that as the pressure increases, the absolute value of charge for As and Fe atom increases while Cr remains nearly a constant, indicating that the mechanic properties of FeCrAs under pressure should be mostly attributed to the interaction between Fe and As atoms.
author_names: Dewei He

Yongjin Peng

Yongjin He
title: Ab Initio Studies on Structural, Elastic, Thermodynamic and Electronic Properties of FeCrAs under Pressures
year: 2015