Structural, mechanical, electronic and thermodynamic properties of VH2 for hydrogen storage purposes

Abstract

First principles calculations have been carried out to study structural stability of the cubic (Fm3‾ m), orthorhombic (Pnma) and tetragonal phases (I4/mmm and P42/mnm) of VH2 in which structural, elastic, mechanical, anisotropic, electronic and thermodynamic properties are determined. The evaluation of computed elastic constants related to the phases revealed that the Fm3‾ m, Pnma and I4/mmm phases exhibit mechanical stability based on the stability criteria whereas P42/mnm phase is found mechanically unstable. B/G ratio, Cauchy pressures and Poisson's ratio showed that all phases are ductile in nature. Elastic anisotropy, machinability index, hardness, melting temperatures are obtained and analysed in depth. The electronic band structures illustrated metallic character. 3D curves of linear compressibility, Young's modulus, Shear modulus, and Poisson's ratios of phases showed elastic anisotropy except for linear compressibility. The thermodynamic properties are also obtained between 0 and 800 K. Debye vibrational energy, vibrational free energy, entropy and heat capacity are analysed.