Effect of the thermodynamic factor on the intrinsic and tracer diffusivities in binary mixtures

MS Puelles and M Hoyuelos, PHYSICAL REVIEW E, 107, 024123 (2023).

DOI: 10.1103/PhysRevE.107.024123

One of the Darken equations gives a relationship between the intrinsic and the tracer diffusion coefficients, DA and D*A, of species A in a solid binary mixture. In its original formulation, the equation reads DA = D*A , with  the thermodynamic factor. The question addressed in this paper is how DA and D*A depend separately on . Using a recent result for transition probabilities in terms of the excess chemical potential M. Di Muro and M. Hoyuelos, Phys. Rev. E 104, 044104 (2021), it is shown that the intrinsic diffusivity does not depend on . This approach simplifies a previous theoretical analysis that reaches the same result. Experimental results of diffusion in Ni-Pd and Fe-Pd alloys M. J. H. van Dal et al., Acta Mater. 48, 385 (2000) are used to check the theory. Numerical simulations of Ni-Pd were performed to show that the migration energy is the main factor responsible for the increase in diffusivity at intermediate concentrations.

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