Full-Potential KKR Calculations for Point Defect Energies in Metals, based on the Generalized-Gradient Approximation: I. Vacancy Formation Energies in fcc and bcc Metals

Abstract

We present systematic first-principles calculations for vacancy formation energies E_V^F in most of elemental metals (Li∼Au) of fcc and bcc structures, as well as bulk properties such as lattice parameters a and bulk moduli B. The calculations are based on the generalized-gradient approximation in density-functional formalism, proposed by Perdew and Wang in 1991 (PW91-GGA), and apply the full-potential Korringa-Kohn-Rostoker Green’s function method for perfect crystals and point defect systems, developed by the Jülich group. First we show that the calculated bulk properties for all elements studied are in excellent agreement with the experimental results: the PW91-GGA corrects the deficiencies of the local spin density approximation for metals, i.e., the underestimation of a and the overestimation of B and the theoretical errors in a and B are reduced within ∼ 1% and ∼ 10% of experimental results, respectively. Second we show that E_V^F for most of fcc metals are reproduced within the experimental errors, while E_V^F for most of bcc metals are overestimated by 10%–20% of the experimental results. It is noted that the comparison with the experimental results needs the inclusion of the thermal lattice expansion effect in the first-principles calculations because most of the experimental results were derived from positron annihilation measurements at high temperatures. The remaining discrepancies between theory and experiment are also discussed.