EQUATIONS OF STATE FOR THE LENNARD-JONES MIXTURES AT HIGH-TEMPERATURES

The virial coefficients for binary mixtures at high temperatures were directly calculated up to the fifth term by use of a Monte-Carlo integration technique and the various empirical mixing rules that have been proposed for estimating mixture virial coefficients were tested. It was found that these empirical mixing rules tend to fail as the molecular size differences increased. Accurate compressibility of the Lennard-Jones binary mixtures were also calculated by adopting Metropolis Monte-Carlo simulations in order to examine validity of the fifth order virial equation of state. At high temperature (T* = 20), the compressibility factors calculated by the fifth order virial equation of state were in good agreement with the results of the simulations in the range of V/b greater-than-or-equal-to 0.4 (b = 2-pi-sigma-3N(a)/3). It was also found that the van der Waals one fluid theory could provide accurate compressibility factors even for mixtures of molecules with large size differences at high temperatures.