Based on our previously developed solid-liquid-vapor equation of state (EOS), we have calculated phase equilibria of benzene, cyclohexane, and their mixtures. The model predictions for phase behaviors of pure compounds and vapor-liquid phase equilibria of the binary system have been straightforward and agreed well with the reported data. However, solid-liquid phase equilibria of the binary system are not well correlated to the experimental data with the present unified EOS model. Then, from this fact, we have found that the coexisting solid phases in the present binary system exist in two different solid structures (or two different Gibbs free-energy curves). We have developed a model to overcome such a problem within the present unified EOS model and successfully correlated the experimental data for wide ranges of temperatures and pressures. (c) 2004 Elsevier Ltd. All rights reserved.