High orders corrections to the Van der, Waals–London forces. I. A model problem: Two interacting hydrogen molecules is the minimal basis set

Abstract

AbstractThe classical intermolecular Rayleigh‐Schrödinger perturbation expansion is used with a finite basis of simple products of single determinants. For two hydrogen molecules with a minimal basis set, one shows that the ring and ladder diagrams dominate the perturbation series. The contributions of the purely intermolecular convex and concave ring diagrams are summed at all orders. The mixed ladder‐ring diagrams are also included. The series converges if the norm of the first order perturbed wave function is smaller than ½. The summation multiplies the Van der Waals–London forces by an explicit factor.