Nonexpanded coupled Hartree-Fock approach to evaluation of three-body induction energies

A method for the calculation of the nonexpanded three-body second- and third-order coupled Hartree-Fock induction energies is developed. Both the long-range multipolar contributions as well as the short-range penetration effects are taken into account. The latter are shown to be significant in certain cases. The relationship between perturbative induction energies and the supermolecule deformation energy is discussed. The equivalence of the two approaches is demonstrated in the region of small intermolecular overlap. Illustrative calculations are reported for (H2O)3 and Ar2HCl.