Diffusion under Large Driving Forces

摘要

In the diffusion literature the classical Nernst-Einstein equation is used to describe the effect of driving forces. This implies that the diffusive flux is proportional to the driving force. However, this linear law will not be valid if the driving force is very large. Attempts in the literature for the derivation of an "improved relation" till now were restricted to the cases when the diffusion coefficient was independent of the composition. On the other hand, it is also known that even if no driving forces (other than related to the chemical driving force) are present then deviations from the Fick I law are expected on nanoscale. In this lecture attempts will be made to find a general description for the above problems, i.e. when the driving forces and the diffusion asymmetry (the composition dependence of the diffusion coefficient) are large.