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

Abstract

Herein, the high‐pressure impacts on the electronic, mechanical, and thermodynamic properties of MAX‐phase M2GaC (M = Nb and Ta) are calculated through the first principles. The phonon dispersion results indicate that M2GaC (M = Nb and Ta) is dynamically stable. The elastic constants and elastic modulus of Nb2GaC and Ta2GaC increase with the pressure increase, while the elastic anisotropic 3D surface structure and projection diagram show that bulk modulus, shear modulus, and Young's modulus all show anisotropy. M2GaC (M = Nb and Ta) has metallic, covalent, and ionic bonds. In addition, based on the quasiharmonic Debye model, the effects of high pressure (0–50 GPa) and temperature (0–2000 K) on the thermodynamic properties of Nb2GaC and Ta2GaC are systematically studied. The constant pressure heat capacity (CP) and thermal expansion coefficient (α) of Nb2GaC and Ta2GaC decrease with the increase of pressure, while the internal energy (U) and Gibbs free energy (G) of Nb2GaC and Ta2GaC increase with the increase of pressure. The sound velocity and kmin increase with the pressure increase, and Nb2GaC has a higher thermal conductivity than Ta2GaC.