(68f) Two-Phase Molecular Dynamics Simulations of n-Propane Vapor-Liquid Equilibria

A molecular dynamics (MD) method [Fern et al., J. Phys. Chem. B 2007, 111, 3469.] recently developed for determination of phase equilibrium in a single, two-phase simulation has been shown to be accurate even near the critical point because complete phase separation and no particle insertions are required. In this work, we modify the method for structured molecules by employing a Monte Carlo (MC) method to determine the associated volume for every particle in the simulation cell. Bulk liquid and vapor densities are then determined by comparing the molecular volume distributions of liquid and vapor in the two-phase simulations to those obtained in single-phase simulations. Two-phase molecular dynamic (MD) simulations were performed on n-Propane using a Transferable Potential for Phase Equilibria (TraPPE) model. The coexisting liquid and vapor densities obtained agreed well with literature values from Gibbs Ensemble Monte Carlo (GEMC) simulations.