Influence of gradient corrections to the local-density-approximation on the calculation of hyperfine fields in ferromagnetic Fe, Co, and Ni.

Abstract

Results of hyperfine field calculations for ferromagnetic bcc Fe, fcc Co, and fcc 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 presented. Especially the influence of gradient corrections on the electronic 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 the radius r approaches 0. However, it has only little impact on the hyperfine fields, although pronounced changes in the charge densities in the nucleus-near region are observed. While the hyperfine fields calculated 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 experiment. \textcopyright{} 1996 The American Physical Society.