First Principles Study of the LiNH2/Li2NH Transformation

On the basis of ab initio simulations, we propose a scenario for the decomposition pathway of Li amide into Li imide and ammonia (2LiNH(2) -> Li2NH + NH3) which represents the first step of the dehydrogenation reaction of the LiNH2/LiH3 mixture. Activation energies for formation of NH3 in LiNH2, for diffusion of charged species (H+, Li+) in LiNH2 and Li2NH, for H+/Li+ transfer across the LiNH2/Li2NH interface and for NH3 desorption at the surface of LiNH2 and Li2NH have been computed from first principles. The results actually suggest that the transformation path depends on the surface-to-volume ratio of the LiNH2 crystallites.