Monte Carlo simulation of fluid phase equilibria in pore systems: square-well fluid distributed over a bulk and a slit-pore

An extension of the Gibbs ensemble simulation technique is presented, which permits the simultaneous treatment of multiple fluid-phase equilibria involving a bulk and a confined fluid. The method incorporates separate phase simulation boxes for the two regions and possible coexisting phases within each region. We perform three-box Gibbs simulations for subcritical bulk square-well fluids at equilibrium between a bulk and a hard planar slit region. We compare our results with grand canonical simulation data on supercritical conditions when each region contains only a single phase, and calculate coexistence densities for three-phase states at bulk gas-liquid equilibrium.