Ab initio molecular dynamics study of the hydrogen diffusion in sodium and lithium hydrides

Light weight complex metal hydrides, sodium hydride (NaH), and lithium hydride (LiH) are the last step materials during hydrogen release process of alanates and borates, which are promising candidates for hydrogen storage. We report ab initio molecular dynamics (MD) calculations based on density functional theory to study the hydrogen-deuterium exchange in NaH and LiH. We predict the single hydrogen-deuterium exchange in NaH and LiH and calculate the self-diffusion constants, << D >>(NaH)approximate to 1.46x10(-9) m(2) s(-1) of deuterium in NaH at 420 K and << D >>(LiH)approximate to 1.49x10(-9) m(2) s(-1) of deuterium in LiH at 550 K, which are in good agreement with the experimental values.