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

Abstract The first-principles calculations are presented for the vacancy formation energies ( E V F ) in the nonmagnetic and ferromagnetic states (NM and FM) of Ni (FCC) and Fe (BCC). The calculations are based on density-functional theory (DFT) and the full-potential Korringa–Kohn–Rostoker Green's function method for impurities. The non-local effect (NLE) beyond the local-spin-density approximation for DFT is taken into account within the generalized-gradient approximation of Perdew and Wang (PW91-GGA). The magnetism, being the difference of FM- E V F with NM- E V F , is large (∼0.6 eV) for Fe, but small (∼0.1 eV) for Ni, while the NLE is large (∼0.6 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 .