Non-additive three body contributions to the lattice energies of nitrogen and carbon dioxide

Abstract

The triple-dipole term in the non-additive three body contributions to the 0 K lattice energy has been evaluated for systems of axially symmetric molecules crystallizing in the f.c.c. (α-N₂) lattice structure. Stogryn's expressions for the triple-dipole energy of non-spherical molecules were used in lattice summations over 24 shells of neighbours. For α-N₂ and CO₂ these results were used to estimate the associated non-additive energy, which was found to be significant, about 6 per cent of the experimental sublimation energy in each case, but the effect of the molecular anisotropy on the triple-dipole energy was found to be quite small.