Relativistic Hartree–Fock by means of stationary direct perturbation theory. II. Ground states of rare gas atoms

The combination of relativistic Hartree–Fock theory with stationary direct perturbation theory presented in paper I of this series is applied to the ground states of the rare gas atoms He, Ne, Ar, Kr, Xe, Rn, in STO basis sets with finite nuclei. The error of the truncation of the perturbation expansion at O(c−6)—with the nonrelativistic reference O(c0)—is only ≊1% for Rn and <0.1% for Xe. The corresponding error for truncation at O(c−2) is <1% for Ar. An approximation in which c−2E(2) is calculated exactly, but in which two electron contributions to c−4E(4) and c−6E(6) are neglected, performs almost as well as rigorous perturbation theory up to c−6E(6) but is computationally much cheaper.