On the Calculation of Arbitrary Multielectron Molecular Integrals Over Slater-Type Orbitals Using Recurrence Relations for Overlap Integrals. II. Two-Center Expansion Method

Abstract

Using expansion formulas for the charge-density over Slater-type orbitals (STOs) obtained by the one of authors the multicenter molecular integrals with an arbitrary multielectron operator are expressed in terms of the overlap integrals with the same screening parameters of STOs and the basic multielectron two-center Coulomb or hybrid integrals with the same operator. In the special case of two-electron electron-repulsion operator appearing in the Hartree-Fock-Roothaan (HFR) equations for molecules the new auxiliary functions are introduced by means of which basic two-center Coulomb and hybrid integrals are expressed. Using recurrence relations for auxiliary functions the multicenter electron-repulsion integrals are calculated for extremely large quantum numbers.