Pressure Dependence of Mechanical and Thermodynamic Properties of MAX‐Phase M₂GaC (M = Nb and Ta) from First‐Principles Calculations

Abstract

In this work, the high‐pressure impacts on the electronic, mechanical and thermodynamic properties of MAX phases M2GaC (M=Nb and Ta) were calculated through the first‐principles. The phonon dispersion results indicate that M2GaC (M=Nb and Ta) are dynamically stable. The elastic constants and elastic modulus of Nb2GaC and Ta2GaC increased with the pressure increase, while the elastic anisotropic three‐dimensional surface structure and projection diagram show that bulk modulus, shear modulus and Young's modulus all show anisotropy. The M2GaC (M=Nb and Ta) have metallic, covalent and ionic bonds. In addition, based on the Quasi‐harmonic Debye model, the effects of high pressure (0‐50GPa) and temperature (0‐2000K) on the thermodynamic properties of Nb2GaC and Ta2GaC are systematically studied. The constant pressure heat capacity and thermal expansion coefficient of Nb2GaC and Ta2GaC decrease with the increase of pressure, while the internal energy and Gibbs free energy of Nb2GaC and Ta2GaC increase with the increase of pressure. The sound velocity and k min increase with the pressure increase, and Nb2GaC has a higher thermal conductivity than Ta2GaC.This article is protected by copyright. All rights reserved.