The intermolecular dimer potential of non-dipolar linear molecules

The intermolecular potentials of H2, D2, F2, 02, N2 and C02 are examined using three independent estimates:1. The Kihara/Koide method, involving core anisotropy, van den Waals dispersion, quadrupolar interaction and octopolar induction terms.2. The ab initio calculation for dimers of these molecules, using 4 - 31G and 6 - 31G basis sets.3. The atom-atom (R.I.S.M.) method.While some consistent features emerge, there is qualitative disagreement in the majority of approach configurations which implies that the Kihara/Koide potential is overestimating the attractive part of the potential energy surface and underestimating the anisotropy of this surface in comparison with the ab initio method.The atom-atom and Kihara/Koide potentials agree almost quantitatively in the majority of approach configurations, so that the extra electrostatic features considered by Kihara et al seem generally to have little effect on the atom-atom results.