Abstract
When diffusion proceeds in a crystal because of point defects which create or eliminate at discrete sinks, the defects can a priorineither be considered as conservative (zero sink strength) nor as being at local equilibrium (infinite sink strength). We establish the correction to Fick's law to first order in inverse sink strength; this introduces an unusual wavelength dependence of the kinetics, which reflects in the shape of the concentration profile, as demonstrated by model calculations.