PHASE-EQUILIBRIA FOR ASSOCIATING LENNARD-JONES FLUIDS FROM THEORY AND SIMULATION

We present results of Gibbs ensemble simulations for phase equilibria of associating pure fluids and mixtures. Lennard-Jones spheres are used to account for repulsive and dispersive interactions, while anisotropic square well sites are used to account for bonding. We compare these simulation data with predictions of Wertheim's theory for associating fluids. The theory accurately predicts saturation densities and fractions of associated and nonassociated species, except near the critical point. For mixtures, the theory also accurately predicts bubble-point pressures and mole fractions. The theory can also be used to predict the properties of tangent diatomic Lennard-Jones molecules.