FREE-ENERGY AND TRANSPORT-PROPERTIES OF THE GAUSSIAN OVERLAP MODEL - VARIATIONAL APPROACH

The purpose of this paper is to find a method for calculating the free energy and the transport properties of a fluid made up of nonspherica l nonpolar molecules in the dense regime. The model potential used was the Gaussian overlap model with constant E. Our procedure relies on t he assumption that at high densities the behavior of a molecular fluid is dominated by the harsh repulsive forces. Hence, the properties of the fluid can be given in terms of an effective hard core fluid. Thus, the free energy was obtained through a variational method with the ai d of a nonspherical reference potential. The results were compared wit h molecular dynamics calculations and with calculations using a pertur bation method. These results are in a close agreement with simulation data. In a further level of approximation the transport properties, th ermal conductivity and shear viscosity, can be estimated with an exten sion of the effective-diameter hard-sphere theory. The results of our calculations for transport properties were compared with experimental data, and with calculations using the effective-diameter hard-sphere t heory, but with effective diameters coming from perturbation theory. I n particular, for the case of shear viscosity the results were excelle nt. For thermal conductivity the results are not that good, however, t he sources of discrepancy are discussed.