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

Recent technical improvements in the molecular dynamics (MD) simulation tec hnique have led to re-evaluation of the transport properties of fluids conf ined in narrow capillary pores of several molecular diameters in width (or nanofluids). Coincident with these developments, it has also become clear t hat unambiguous predictions of the transport properties of nanofluids may o nly be made when a rigorous analysis based on statistical mechanical theory is considered in conjunction with molecular simulation studies. In this pa per, the theoretical analysis embodied in the Pozhar-Gubbins [L.A. Pozhar a nd K.E. Gubbins, J. Chem. Phys., 99 (1993) 8970; L.A. Pozhar and K.E. Gubbi ns, Phys. Rev., E56 (1997) 5367] statistical mechanical theory of transport in strongly inhomogeneous fluid mixtures is combined with nonequilibrium a nd 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 parameter s should be taken into consideration to reliably predict the diffusion flux es within zeolitic systems. For the comparatively simple pore structure exa mined in this work, the local self-diffusivity varies significantly in magn itude over nanometer length scales with corresponding implications for the interpretation of the rate processes taking place within crystalline nanopo rous media. (C) 2001 Elsevier Science B.V. All rights reserved.