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.
Source:
PAC, 1999, 71, 1307
(Definitions of Terms for Diffusion in the Solid State)
on page 1310