Ab initio fitted potentials representing n-pentane/n-pentane and n-pentane/silicalite-1 interactions were newly developed at the second-order Moller-Plesset perturbation (MP2) level with the 6-31G* basis set. Characteristics of the functions were illustrated in comparison with available force field models. They were, then, applied for the molecular dynamics simulation of n-pentane in silicalite-1. The diffusion coefficients are in satisfactory agreement with the results of PFG-NMR experiments. The effect of the box size was also examined. It was found that the components of the diffusion tensor are very sensitive to this parameter. The structure of the n-pentane in the silicalite-1 pore was analyzed in terms of radial distribution functions. The first peak at 4.1 Angstrom indicates the optimal diffusion route of the n-pentane along the central line of the channel of the silicalite-1. (C) 2004 Elsevier B.V. All rights reserved.