Energetics of the Li amide/Li imide hydrogen storage reaction

A density functional theory investigation of the recently identified hydrogen storage reaction LiNH2+LiH <-> Li2NH+H-2 is described. The electronic structure and enthalpy of formation Delta H of each constituent are calculated in both the generalized gradient approximation (GGA) and the local density approximation (LDA). Zero point energies and finite temperature corrections to Delta H are derived via calculation of the vibrational spectra. We find that the GGA provides much more favorable agreement with experiment than the LDA for the structural parameters and for Delta H(LiNH2), Delta H(LiH), and the overall reaction enthalpy.