Higher dispersion coefficients: Accurate values for hydrogen atoms and simple estimates for other systems

The dispersion coefficients Cn (n≤30) and Z(l,λ,L) (l+λ+L≤13) which appear in the multipole expansions of the pair and nonadditive three-body interaction energies, respectively, are calculated to an accuracy of no less than 15 decimal digits for interactions among ground state hydrogen atoms. The pseudostate technique used is as simple and accurate as the momentum-space method recently advocated for this problem. The oscillator and hydrogenic models are used to obtain simple formulas for the estimation of higher dispersion coefficients from two or three of the leading coefficients. These formulas should prove useful in models of intermolecular potentials.