Direct calculation of the Hartree–Fock interaction energy via exchange–perturbation expansion. The He … He interaction

Abstract

Abstract The Hartree‐Fock ( HF ) equations for the (He) 2 system are solved using a suitable exchange perturbation technique. The HF interaction energy is then obtained directly from a rapidly convergent iteration procedure. The method remains convergent for short interatomic distances, where the interaction energy surpasses the energy of intraatomic excitations. The fast convergence of the method is a result of the proper treatment of the exchange‐deformation effects. In the region of the van der Waals minimum, these effects account for 50% of the HF deformation energy.