Diffusion kinetics in the B2-type lattice: Isotope effect and correlation effect

Abstract

The diffusion coefficients of A and B atoms in the B2-type alloy are derived for the case when the six-jump vacancy cycle is operative. On the basis of the analytical expression for the diffusion coefficients in terms of frequencies for individual vacancy jumps, the isotope effect is discussed quantitatively.

The correlation effect in the six-jump cycle is better understood by considering that the effect consists of a microscopic correlation effect and a macroscopic correlation effect. The former refers to the correlation between individual jumps involved in the six-jump cycle, for which the correlation factor can be neither defined nor calculated. The microscopic correlation effect, however, is automatically and correctly taken into account in the expression for the effective frequency for the six-jump cycle derived in this paper.