Study of the Effects of Strain on the Physical Properties of the Metallic Hydride VH2 for Solid-State Hydrogen Storage Applications

In this study, we investigate the effect of triaxial strain ranging from-8% to +8% on the properties of the VH2 compound using Density Functional Theory (DFT). For the unstrained structure, geometric optimization gave a lattice parameter of 4.209 angstrom. This compound is mechanically, dynamically, and thermodynamically stable, as indicated by the Born stability criteria, the absence of imaginary phonon modes, and the negative formation energy, respectively. The hydrogen storage capacities, in terms of gravimetric and volumetric values, are 3.8 wt% and 179.81 kgH2/m3, respectively. The application of a compressive strain of epsilon = -8% increases the volumetric capacity to 230.92 kgH2/m3, and the desorption temperature is reduced to 213.40 K, which is close to ambient conditions, thus making the compound ductile, while maintaining its metallic nature, as confirmed by the band structure and density of states (DOS) analysis. These results highlight the potential of VH2 as a promising material for hydrogen storage applications.