INFLUENCE OF GRADIENT CORRECTIONS TO THE LOCAL-DENSITY-APPROXIMATION ON THE CALCULATION OF HYPERFINE FIELDS IN FERROMAGNETIC FE, CO, AND NI

Results of hyperfine field calculations for ferromagnetic bcc Fe, fee Co, and fee Ni based on the scalar relativistic Korringa-Kohn-Rostoker Green's-function formalism and using various parametrizations for the exchange-correlation energy and the corresponding potential are prese nted. Especially the influence of gradient corrections on the electron ic structure in the nucleus-near region is investigated. The resulting exchange potentials using these generalized gradient approximations ( GGA) lead to the necessity to introduce a finite nucleus model instead of a point nucleus. This procedure removes the divergencies inherent in the general expression for the exchange potential of the GGA's as t he radius r approaches 0. However, it has only little impact on the hy perfine fields, although pronounced changes in the charge densities in the nucleus-near region are observed. While the hyperfine fields calc ulated with one of the GGA's are in general higher than those for the local parametrizations, they are still 16-24% too low compared with ex periment.