Self-diffusion in n-alkane fluid models

Molecular dynamic simulations of fluid n-pentane and n-decane have been performed in order to analyze the self-diffusion. An isotropic united-atom (UA) model as well as anisotropic united-atom (AUA) models have been used to represent the molecular interactions. Self-diffusion coefficients have been calculated. The sensitivity of the self-diffusion coefficient to the shape of the intermolecular potential as well as the torsion potential has been analyzed. The simulation results for the diffusion coefficient are in excellent agreement with experimental data when the molecular interaction is represented by an anisotropic United-Atom model and the internal rotation is governed by a torsion potential proposed in this work.