Consideration was given to an atomistic kinetic approach to the concept that dopant migration in solids occurred via sites which were suitable for occupation by dopants. By using this concept, it was found that Darken’s equation led to a link between the Fickian diffusion coefficient of an ideal solution and the activity coefficient of a non-ideal solution; which had previously been ignored. Einstein’s relationship, which linked the Fickian diffusion coefficient to the mobility of dopants, proved to be true even in the case of non-ideal solutions. The supposed vacancy-wind effect, and the diffusion of dopant-defect pairs as molecule-like complexes were shown to be physically unrealistic. The Orlowski dopant-flux formula proved to be false.

Darken’s Equation and Other Diffusion Relations in the Light of Atomistic Kinetic Concepts. K.Maser: Journal of Solid State Electrochemistry, 1999, 4[1], 3-16