Computer simulation and perturbation theory of fluids modelled using three- and six-site Lennard-Jones potentials

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Abstract
Systematic NVT molecular dynamics simulations have been performed for pure fluids of nonspherical molecules modelled using a triangular three-site and a hexagonal six-site Lennard-Jones (12:6) potential in order to obtain thermodynamic properties of these fluids, particularly the residual Helmholtz free energy. Molecular geometries, shown earlier to work well for propane and benzene, have been utilized in this study. Free energy values obtained from these simulations have been compared with predictions from the reference fluid simulations in a Weeks-Chandler-Andersen type site-frame perturbation expansion to the first order. Comparisons clearly show this site-frame expansion to work well at high densities and no significant effect of molecular anisotropy has been found on the deviations of these predictions, from the exact simulation values, vis-á-vis the WCA theory for the Lennard-Jones (12 : 6) fluid.