Computer simulation of moderately dense hard-sphere fluids and mixtures in microcapillaries

Abstract

Grand canonical ensemble Monte Carlo and molecular dynamics simulations of partitioning and diffusion of rigid sphere fluids and mixtures in cylindrical pores have been carried out for a wide range of pore sizes. The formal linear diffusion theory employed in an earlier paper is extended to binary mixtures and is used to analyse the simulation data. The results obtained show that continuum-mechanical theory may be used to quantitatively predict the diffusion fluxes of small, nonadsorbing solutes as well as macromolecular solutes in micropores as long as the sum of the solute and solvent particle sizes is less than the size of the pore. In addition, the existence of viscous slip for dense fluids observed earlier is confirmed, and it is shown that selective partitioning of solutes in simple fluid mixtures can lead to solvent diffusion barriers in very small pores.