Generating van der Waals coefficients to arbitrary orders of the atom-atom interaction

A recursion procedure is presented for deriving the dispersion coefficients Cs(k) of the van der Waals interaction between two atoms in spherically symmetric ground states to arbitrary high orders k of perturbation theory. The complete asymptotic expansion for the dispersion interaction between two ground-state hydrogen atoms up to C30 (including terms arising from tenth order perturbation theory) are then generated using a pseudo-state expansion for the two atom Green's function.