It was recalled that, when diffusion occurred because of point defects which created or eliminated discrete sinks, the defects could not be considered a priori to be conservative (zero sink strength) or in local equilibrium (infinite sink strength). A correction to Fick's law was made, to first order, in the inverse sink strength. This introduced an unusual wavelength dependence of the kinetics, which was reflected in the shape of concentration profiles.

Diffusion in Crystals with Non-Conservative Defects. G.Martin, C.Desgranges: Europhysics Letters, 1998, 44[2], 150-5