Calculation of the phenomenological coefficients for diffusion by six jump cycles in non-stoichiometric intermetallic compounds

Abstract

In this paper, the six-jump-cycle mechanism, which was conceived as a minimum-energy-penalty sequence of jumps for certain stoichiometric alloys showing antistructural disorder, is extended and employed to calculate the phenomenological coefficients for diffusion at non-stoichiometric compositions for alloys taking the B2 structure. We adopt an analogue of the five-frequency model for impurity diffusion by using antistructural atoms as the ′impurity′ and the six-jump cycle as the diffusion mechanism unit. We frame the formalism in the Ising alloy model. We derive asymptotic (T → 0) expressions for the phenomenological coefficients. The results obtained are in excellent agreement with Monte Carlo computer simulations.