Molecular simulation of phase equilibria: simple, ionic and polymeric fluids

Recent advances in molecular simulation methodologies have enabled the calculation of phase equilibria for model fluids with unprecedented speed and accuracy. In this paper, we first briefly review the Gibbs ensemble Monte Carlo method for direct determination of phase coexistence. A new application of the Gibbs ensemble technique to the restricted primitive model of ionic systems is described in detail. The calculated phase coexistence envelope is in disagreement with most previous theoretical and numerical estimates. Our result for the reduced critical temperature is T_c^* = 0.056 and for the reduced critical density ρ{variant}_c^* = 0.04. A recently developed technique for the calculation of the chemical potentials of polymeric fluids is also discussed and a tentative phase diagram for a homopolymer of length n = 20 segments is presented. We conclude with a discussion of potential future applications of molecular simulation techniques to the prediction of equilibrium properties of fluids.