London dispersion coefficients from static multipole polarizabilities

Abstract

Second order variational calculations of static dipole, quadrupole and octupole polarizabilities have been performed at the ab initio level for the ground states of H, He, Li, Be, Na, Mg using Hartree-Fock ω₀ and the whole atomic hamiltonian as ℋ₀. In the frozen core approximation only valence electrons are excited to a few optimized pseudostates of appropriate symmetry. For alkaline earth atoms a limited but properly shaped electron correlation is introduced through simple configuration interaction in the ground and in the excited state. The resulting multipole polarizabilities with their associated excitation energies allow for the one-centre calculation of C₆, C ₈, C ₁₀ dispersion coefficients for all possible pairs of atoms through use of the generalized London formula. The numerical results compare favourably with those from accurate calculations.