Improved a b i n i t i o effective potentials for Ar, Kr, and Xe with applications to their homonuclear dimers

Effective core potentials for the Ar, Kr, and Xe atoms derived from numerical Hartree–Fock and Dirac–Hartree–Fock wave functions are applied in SCF and CI calculations of homonuclear diatomic potential energy curves. Detailed comparisons are made with the all-electron calculations of Wadt for the ground and lowest positive states. Relativistic effects, excluding spin–orbit coupling, are seen to be relatively unimportant. Plots of the potential energy curves and computed spectroscopic constants show excellent agreement with the all-electron results. On the other hand, comparisons with results obtained using effective potentials derived using varients of Phillips–Kleinman procedures show dramatic differences for Xe2 and Xe2+. From SCF calculations on Xe2 and Xe2+ it was found that the explicit inclusion of the spin–orbit operator in the SCF procedure (using ω–ω coupling) results in essentially the same potential curves obtained by adding the spin–orbit correction as a final semiempirical perturbation.