First-principles calculations for vacancy formation energies in Ni and Fe:non-local effect beyond the LSDA and magnetism

The first-principles calculations are presented for the vacancy formation e nergies (E-V(F)) in the nonmagnetic and ferromagnetic states (NM and FNI) o f Ni (FCC) and Fe (BCC). The calculations are based on density-functional t heory (DFT) and the full-potential Korringa-Kohn-Rostoker Green's function method for impurities. The non-local effect (NLE) beyond the local-spin-den sity approximation for DFT is taken into account within the generalized-gra dient approximation of Perdew and Wang (PW91-GGA). The magnetism, being the difference of FM-E-V(F) with NM-E-V(F), is large (similar to0.6 eV) for Fe , but small (similar to0.1 eV) for Ni, while the NLE is large (similar to0. 6 eV) for both transition metals. We found that the measured E-V(F) at high temperatures, corresponding to E-V(F) in the paramagnetic state, is close to the calculated NM-E-V(F). (C) 2001 Elsevier Science B.V. All rights rese rved.