Perturbation calculations of molecular interaction energies: an example, HF....HF

Abstract

An expression for the interaction energy of two molecules, obtained by expanding the wavefunction for the whole system in terms of antisymmetrized products of free-molecule functions and using a matrix perturbation scheme, is used in ab initio calculations on the HF dimer. The computed interaction energy is fitted with considerable accuracy by a simple analytical formula. The equilibrium geometry and hydrogen-bond energy are in satisfactory agreement with available experimental results.