Self-diffusion in a fluid confined within a model nanopore structure

Abstract

Recent technical improvements in the molecular dynamics (MD) simulation technique have led to re-evaluation of the transport properties of fluids confined in narrow capillary pores of several molecular diameters in width (or nanofluids). Coincident with these developments, it has also become clear that unambiguous predictions of the transport properties of nanofluids may only be made when a rigorous analysis based on statistical mechanical theory is considered in conjunction with molecular simulation studies. In this paper, the theoretical analysis embodied in the Pozhar–Gubbins [L.A. Pozhar and K.E. Gubbins, J. Chem. Phys., 99 (1993) 8970; L.A. Pozhar and K.E. Gubbins, Phys. Rev., E56 (1997) 5367] statistical mechanical theory of transport in strongly inhomogeneous fluid mixtures is combined with nonequilibrium and equilibrium molecular dynamics techniques to investigate self-diffusion in a dense fluid confined within a model crystalline nanopore. The results obtained demonstrate that the spatial dependence of the transport parameters should be taken into consideration to reliably predict the diffusion fluxes within zeolitic systems. For the comparatively simple pore structure examined in this work, the local self-diffusivity varies significantly in magnitude over nanometer length scales with corresponding implications for the interpretation of the rate processes taking place within crystalline nanoporous media.