First-principles calculations of phase stability, electronic structure, mechanical properties and thermal conductivities of TMH2 (TM=V, Nb, Ta) metal hydrides

TMH2 (TM = V, Nb, Ta) metal hydrides can be used as potential hydrogen storage materials. However, there have been no available data on the mechanical and thermodynamic properties of these hydrides, especially TaH2. Herein, based on first-principles calculations, the phase stability, electronic structure, mechanical properties and thermal conductivities of TMH2 (TM = V, Nb, Ta) hydrides are investigated. The results show that VH2, NbH2, and TaH2 are thermodynamically and dynamically stable. The calculated electronic structures show that these three hydrides possess electron orbital hybridization among atoms and strong chemical bonding. The chemical bonds in TMH2 are mainly ionic and partially covalent. According to the calculated Poisson's ratios, Pugh's ratio and Cauchy pressures, VH2, NbH2, and TaH2 are ductile. Moreover, these three hydrides have elastic anisotropy and good damage tolerance. Finally, the predicted thermodynamic properties indicate that TMH2 can be used as potential thermal insulating materials.