Perturbation theory for high pressure behavior of liquid mixtures

Pade approximant to the Helmholtz free energy was developed for mixtures of nonspherical molecules. Comparisons of the theory with computer simulation results show the equation to be highly accurate for fluids in which strong polar, quadrupolar or anisotropic overlap forces are present. The theory is shown to work well in both the gas and liquid states. Mixture properties calculated include the excess thermodynamic functions, the vapor-liquid coexistence curves (compositions and pressures), the liquid-liquid coexisting curves (where present), and the vapor-liquid critical loci. Comparisons of theory with experiment are reported for pure fluids, binary systems and ternary systems.