Computer simulation of phenomenological coefficients for atom transport in a random alloy

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Abstract
Linear‐response theory provides general formulae for the phenomenological coefficients for atom transport defined by non-equilibrium thermodynamics. These formulae can be written in forms which are simple generalizations of the Einstein formula for tracer diffusion; they can therefore be calculated in a similar manner to tracer diffusion coefficients by Monte Carlo simulation of a system at thermodynamic equilibrium. The method is applied to calculate the phenomenological coefficients LAA, LBB , and LAB =LBA for a random f .c.c. alloy of components A and B with a very small concentration of vacancies. The diffusion coefficients of A and B are simply related to these coefficients. Compared with the simulation calculation of tracer correlation factors, larger numbers of vacancy jumps are needed to obtain acceptable statistics, particularly for the cross-coefficient LAB- The results are in agreement with the theory of Manning (1971) within the accuracy attained.