Mechanical properties and hydrogen diffusion behaviors of metal hydrides from molecular dynamics simulations

Based on density functional theory calculations, the elastic mechanical properties and kinetic diffusion behaviors of hydrogen in cubic and tetragonal metal hydrides MH2 (M = Y, Sc, Er, La, Ta, Ti, Zr, Hf) and non-stoichiometric phases with vacancies (MH1.75) were investigated using machine learning molecular dynamics. Our research indicates that the elastic modulus of the metal hydrides generally decreases with an increase in temperature. The temperature-dependent elastic properties also indicate the mechanical stability of the tetragonal and cubic phases of TiH2 and ZrH2 at lower and higher temperatures, respectively. Both the temperature and the composition of the material also affect the diffusion coefficient. This study demonstrates that combining elastic modulus measurements with molecular dynamics would be helpful in predicting the response of materials under stress and to compare the properties of metal hydrides in different environments.