Two-centre calculation of dispersion coefficients

Abstract

Ab-initio two-centre calculations of dispersion coefficients up to C 10 for binary systems involving atoms with one or two valence electrons (H, He, Li, Be, Na, Mg) have been performed by a variation-perturbation method used early for dealing with C 6 London coefficients. The method involves simultaneous two-centre optimization of the coupled expression resulting from the asymptotic interaction, using Hartree-Fock unperturbed wavefunctions and simple excited pseudostates plus valence-shell electron correlation for alkaline earth atoms. The results are very close to those obtained from the simpler one-centre method relating dispersion coefficients to the static multipole polarizabilities of the interacting atoms.