A simple two-liquid approximation of lattice theory for modeling thermodynamic properties of complex fluids

A simple equation of state (EOS) applicable to complex fluids was formulated based on the nonrandom two-liquid approximation of lattice-hole theory. The EOS requires two molecular parameters representing molecular size and interaction energy for a pure fluid, and one additional interaction parameter for a binary mixture. The model quantitatively describes configurational properties of pure fluids and phase equilibria behaviors of mixtures. It gives a good phase equilibria description even for liquid-liquid equilibria of systems containing simple, complex or macromolecular species. To our knowledge, no other approximate molecular theory originating from the classical lattice theories has been presented which describes the entire range of configurational properties of fluids from a practical point of view, although the formulation of the EOS was based on a phenomenological argument in a sense.