A non-equilibrium molecular dynamics method for simulating flow and diffusion within membranes was presented. The method involved two fixed volumes, separated by the permeable medium, which were maintained at fixed, though different, chemical potential. By monitoring the flow and diffusion of the fluid particles through the non-equilibrium interstitial region one could simulate mass transfer processes in a manner which parallels real laboratory experiments. The method was applied to a simple microporous membrane system and it was shown that slip flow, rather than viscous shear, was the predominant mechanism governing the permeation of moderately dense hard-sphere fluids in very fine pores.

Nonequilibrium Molecular Dynamics Simulation of Diffusion and Flow in Thin Microporous Membranes. MacElroy, J.M.D.: The Journal of Chemical Physics, 1994, 101[6], 5274-80