The H-D isotope effect in the stability of lithium alanate

The enthalpies of dehydrogenation of the potential hydrogen storage material LiAlH4 and its deuterated counterpart, LiAlD4, have been calculated using density functional theory at the generalised gradient approximation level and harmonic phonon analysis. While the deuterated structure is predicted to be more stable than LiAlH4, the decomposition of LiAlD4 is still exothermic and spontaneous at low temperatures. The results indicate that LiD should start forming in a sample of Li3AlD6 above 175 K, 17 K higher than the decomposition temperature of Li3AlH6.