Sternheimer antishielding factors of F⁻, Cl⁻, Br⁻ and I⁻: influence of approximate free and crystal ion potentials

Abstract

Sternheimer ionic antishielding factors, γ_∞, have been calculated for F⁻, Cl⁻, Br⁻, and I⁻ in crystals using the Watson model within the nonrelativistic Hartree-Fock approximation and the perturbation numerical procedure. The free ion calculations of γ_∞ using the Hartree-Fock wave functions have also been carried out in order to ascertain the solid-state effects. The free ion values of γ_∞ change from −22.2, −55.1, −135.106, and −248.1 to −10.3, −34.8, −75.6, and −148.7 in solids for F⁻, Cl⁻, Br⁻, and I⁻, respectively. A major part of the discrepancy between the free ionic γ_∞ values based on the Hartree-Fock and Hartree-Fock-Slater wave functions, as noted by the previous workers, is shown to arise from an inaccurate description of the self-interaction potential in the conventional Slater exchange approximation.