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Microscopic approach to the evaluation of diffusion coefficients for substitutional f.c.c. solid solutions

The microscopic theory of atomic diffusion kinetics is used for f.c.c. substitutional solid solutions. Within this approach, the short-range order relaxation is due to the atomic migration. Experimental data on the time dependence of radiation diffuse scattering are used for the determination of microscopic characteristics of atomic migration. The model takes into account the discrete and anisotropic character of atomic jumps in a long-range field of the concentration heterogeneities of interacting atoms. Such a consideration is applied for a close-packed Ni-Fe solid solution. Atomic-jumps' probabilities are estimated that allows to determine the diffusion coefficients and activation energies. Independent kinetic experimental data about a time evolution of long-range order are also used to calculate diffusivities in L12-Ni-Fe alloy.