Study of self-diffusion in metals by statistical moment method: Anharmonic effects

Abstract

The self-diffusion in metals is studied using the moment method in the statistical dynamics including the anharmonicity effects of lattice vibrations. The Gibbs free energy of a metal lattice containing thermal vacancies is derived using the fourth order moment approximation. The interaction energies between the atoms in metals are estimated by using the effective pair potentials. The activation energy Q and pre-exponential factor D0 of the self-diffusion coefficient are given in closed forms. The activation energy Q and pre-exponential D0 values are calculated for Fe, Ag, Ta, and W metals at high temperature region near the melting temperature as well as at low (liquid Helium) temperatures, and they are shown to be in good agreement with the experimental results.