Anisotropic united atom model including the electrostatic interactions of methylbenzenes. II. Transport properties

A new potential model for monoaromatics based an anisotropic united atoms model and three electrostatic charges is used to simultaneously represent the dipole moments, the vapor-liquid equilibrium, the transport properties, and the structural properties while keeping computational effort minimal. The present article focuses on the transport properties and dynamic structural properties. Shear viscosities and diffusion coefficients are computed from equilibrium molecular dynamics in a large range of pressures (0. 1-500 MPa) and temperatures (298-363 K). Viscosity shows a significant improvement with respect to the previous nonpolar models, as average deviations on toluene, p-xylene, ni-xylene, and o-xylene stay below 9%. Self-diffusion coefficients and reorientational diffusion coefficients of toluene are also in good agreement with experimental observations. Thermal conductivity, evaluated by nonequilibrium molecular dynamics, reveals maximum deviations of 8% on benzene, toluene, and xylene isomers, which is better than those of other potentials investigated. By its lower computation time and equivalent accuracy compared with all atoms models, the proposed AUA potential is a good option for investigating complex problems such as the prediction of fuel viscosity in the high-pressure conditions encountered in the injectors of diesel engines.