Superionicity in the hydrogen storage material Li₂NH: Molecular dynamics simulations

We have employed ab initio molecular dynamics simulations in an attempt to study a temperature-induced order-disorder structural phase transformation that occurs in Li₂NH at about 385 K. A structural phase transition was observed by us in the temperature range 300–400 K, in good agreement with experiment. This transition is associated with a melting of the cation sublattice (Li⁺), giving rise to a superionic phase, which in turn is accompanied by an order-disorder transition of the N-H bond orientation. The results obtained here can contribute to a better understanding of the hydrogen storage reactions involving Li₂NH and furthermore broaden its possible technological applications toward batteries and fuel cells.