Theory of Self-Diffusion in Liquid Metals

Abstract

The physical nature of the self-diffusion coefficient in liquid alkali metals is discussed. Self-diffusion coefficient D is represented as the sum of two contributions, namely, single-particle and collective ones. The contribution of the collective component near the melting point is shown to be 5–6% and to increase to 25–30% when the temperature increases to T/T_c = 0.75, where T_c is the critical temperature. The sum of the single-particle and collective contributions reproduces the experimental values and the temperature dependence of the self-diffusion coefficient of a liquid alkali metal at a sufficient accuracy (above 95%). A new method is proposed to calculate the ionic radii of liquid metals and it is based on their shear viscosities. The problem of the applicability of Einsten’s formula is discussed in terms of the similarity principle in order to determine the single-particle contributions to the self-diffusion coefficients of liquids and liquid metals. A new formulation of the similarity principle for liquid metals is proposed.