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Publication
American Journal of Physics
Paper
More on the concentration dependence of Fick's laws
Abstract
We show that concentration-dependent diffusivities that enter Fick's laws can be derived from random-walk models of diffusion. In particular, Darken's phenomenological expression for that dependence results if the transition frequencies depend on the occupation of final states. We develop the one-dimensional discrete-to-continuum passage with some care, and, in particular, we show that fluxes must be defined at the midpoint between lattice sites, even for nonlinear problems.© 1986, American Association of Physics Teachers. All rights reserved.