First-principles calculations for vacancy formation energies in Cu and Al;non-local effect beyond the LSDA and lattice distortion

We show ab initio calculations for vacancy formation energies in Cu and Al. The calculations are based on density-functional theory and the full-poten tial Korringa-Kohn-Rostoker Green's function method for impurities. The non local effect beyond the local-spin-density approximation (LSDA) for density -functional theory is taken into account within the generalized-gradient ap proximation (GGA) of Perdew and Wang. The lattice relaxation around a vacan cy is also investigated using calculated Hellmann-Feynman forces exerted on atoms in the vicinity of a vacancy. We show that the GGA calculations repr oduce very well the experimental values of vacancy formation energies and b ulk properties of Cu and Al, as they correct the deficiency of LSDA results (underestimation of equilibrium lattice parameters, overestimation of bulk moduli, and vacancy formation energies). It is also shown that the GGA cal culations reduce the LSDA results for the lattice relaxation energy for a v acancy in Cu. (C) 1999 Elsevier Science B.V. All rights reserved.