diffusion under the influence of a gradient in chemical composition. In concentrated solid solutions, e.g. A1-xBx
, or in diffusion couples, the motion of one constituent causes a counterflow of the other constituents(s) or vacancies. In this case one can define a diffusion coefficient for the intermixing, which is called the chemical diffusion coefficient or interdiffusion coefficient.
PAC, 1999, 71, 1307. 'Definitions of Terms for Diffusion in the Solid State' on page 1310 (https://doi.org/10.1351/pac199971071307)