NONEQUILIBRIUM MOLECULAR-DYNAMICS SIMULATION OF DIFFUSION AND FLOW INTHIN MICROPOROUS MEMBRANES

A new nonequilibrium molecular dynamics method for simulating flow and diffusion within membranes is presented. The method involves two fixe d volumes, separated by the permeable medium, which are maintained at fixed, though different, chemical potential. By monitoring the flow an d diffusion of the fluid particles through the nonequilibrium intersti tial region one can simulate mass transfer processes in a manner which parallels real laboratory experiments. The method is applied to a sim ple microporous membrane system and it is shown that slip flow, rather than viscous shear, is the predominant mechanism governing the permea tion of moderately dense hard-sphere fluids in very fine pores.