  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.
