Direct calculation of phase equilibria from transition matrix Monte Carlo simulation

The phase behavior of real fluids and model systems is of significant interest to scientists and engineers. In this presentation, an approach for directly determining the phase equilibrium of a model system at any temperature along the coexistence line is described. The approach utilizes information about attempted transitions between states along the Markov chain as opposed to tracking the number of times the chain visits a given state as is done in conventional simulations. The main result from a simulation conducted at a given temperature is a density probability distribution for a range of densities that includes both coexisting phases. Saturation pressures and coexisting densities are calculated in a straightforward manner from the probability distribution. Results will be presented for a variety of systems, including phase coexistence data for pure and binary bulk systems, surface tension values, and phase behavior calculations for systems interacting with one or more surfaces.