An optimization of the carbon force centers connecting the aromatic ring with methyl groups was performed to extend the new Anisotropic United Atoms (AUA) intermolecular potential recently developed for benzene molecules that include electrostatic interactions [Bonnaud, P.; Nieto-Draghi, C.; Ungerer, P. J. Phys. Chem. B 2007, 111, 3730-3741]. The new potential has been tested by computing thermodynamic and structural properties of methylbenzenes using Gibbs Ensemble, NPT Monte Carlo simulations. A comprehensive comparison of the new model is given with other intermolecular potentials taken from the literature. Overall thermodynamic and structural properties of our optimized model are in very good agreement with experimental data, represented by an absolute average deviation of <1% for liquid density, <2% for vaporization enthalpy, and <18% for vapor pressure. The new model also provides a coherent representation of the liquid structure, as revealed by three-dimensional spatial density functions and carbon-carbon radial distribution function. Preliminary calculations of shear viscosity by equilibrium molecular dynamics show a better agreement with experimental data as a result of introducing electrostatic charges in the AUA potential.
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