First-principles study on lithium and magnesium nitrogen hydrides for hydrogen storage

We have investigated the fundamental properties such as structural stability, heat of formation and electronic structure of lithium and magnesium nitrogen hydrides, LiNH2, Mg(NH2)2 and Li2NH, by means of the first-principles calculations using highly precise all-electron full-potential linear augmented plane wave method. The heats of formation involved in the reactions Li2NH+H2↔LiNH2+LiHLi2NH+H2↔LiNH2+LiH are estimated as −63−63 kJ/mol H2 within generalized gradient approximation and −71−71 kJ/mol H2 within local density approximation. Furthermore, we also obtain heats of formation concerning two elementary reactions given by an ammonia mediated model for H2 desorption mechanism.