Assessment of multipolar approximations to the induction energy

Abstract

The induction energy of the van der Waals molecules HCN…HF and H 2CO…HF is calculated using distributed polarizabilities up to hexadecapole rank, and the results are compared with induction energies obtained from a Morokuma analysis using the same basis set. A self-consistent treatment of the induced moments leads to energies that show signs of divergence at short range, and better results are obtained with a simple first-order treatment. The calculations lead to the conclusion that accurate induction energies require distributed polarizabilities, even for quite small molecules, and that it is necessary to include polarizabilities at least to quadrupole rank.