To calculate the heat capacity of the bulk alpha-Li3N, beta-Li3N, LiH, and LiNH2 phases, we calculated the phonon spectrum of each material, using density functional theory (DFT), and then calculated the heat capacity as the sum of the contributions from each phonon, weighted by the phonon density of states. The details of the DFT calculations are given in reference. In addition, we approximated the effect of nanosizing on the heat capacity using the formalism described by Singh et al. for spherical nanoparticles. To do this the number of broken surface bonds per unit area was required, which we counted using the lowest energy surface plane for each material.