On the evaluation of three-centre Hellmann-Feynman force integrals involving Slater-type atomic orbitals

Abstract

A combination of analytical and semi-numerical methods is suggested for the accurate evaluation of three-centre Hellnami-Feynman force integrals occurring in some studies of molecular systems. The analytical method combines the expansion techniques of Coulson (1937) and Bader (1962) while the semi-numerical method employs a double-zeta expansion (Barnett 1963). Explicit analytical expressions are listed for all required non-vanishing integrals involving up to 2s and 2p Slater-type atomic orbitals.