Theory of hyperfine fields of iron

The hyperfine fields of Fe, Ni, Co, and their alloys are calculated by use of nonlocal methods which allow us to go beyond the local density approximation (LDA) of the density functional theory. Two different methods, both belonging to the optimized effective potential method are proposed: the first one is the RPA applied to the Kohn-Sham orbitals, and the second one is the combination of the exact-exchange method for the core states and the LDA for the valence states. Both approaches give much improved description for the hyperfine fields of the magnetic transition metals. Especially for iron, the theory, for the first time, succeeded in predicting reasonable values for the Fermi contact hyperfine fields: -329 kG by the RPA and -394 kG by the combined approach.