SYMMETRY-ADAPTED DOUBLE-PERTURBATION ANALYSIS OF INTRA-MOLECULAR CORRELATION EFFECTS IN WEAK INTER-MOLECULAR INTERACTIONS - HE-HE INTERACTION

A general symmetry-adapted double-perturbation procedure for treating intramolecular or intra-atomic correlation in the theory of intermolecular forces is developed. The method was applied to the interaction of two helium atoms. The calculations were made employing the Møller-Plesset partition of atomic hamiltonians and using a large basis set of explicitly correlated gaussian wave functions. At the van der Waals minimum the total intra-atomic correlation contribution to the interaction energy amounts to — 2 9 K and is mainly due to the change of the dispersion energy. The total interaction energy is equal to —10-3 K being in agreement with the latest experimental result of Burgmans, Farrar and Lee. © 1979 Taylor & Francis Group, LLC.