Soft Coulomb hole for the Hartree-Fock model to estimate atomic correlation energies

An empirical model for the correlation energy ($E_c$) of atoms is proposed. The method, a perturbation applied to the Roothaan Hartree-Fock atomic functions, requires the reevaluation of the two-electron integrals due to the introduction of a ‘‘soft’’ Coulomb hole whose magnitude is calibrated semiempirically. We have tested it by computing the total correlation energy, the first ionization potentials for atoms helium through xenon, by considering excited states of the ground-state configuration for Z=3 to Z=18 and the electron affinity for fluorine, chlorine, bromine, and iodine ions.