(223b) Gibbs Ebsemble Simulation of the Phase Diagrams of Simple Fluids: Ar, Kr, and CH4 Using Temperature Dependent Interaction Parameters

The use of temperature dependent interaction parameters, instead of using temperature independent interaction parameters, may lead to improvement in the prediction of the vapor-liquid coexistence curve. Published second virial coefficient data were used to fit a simple two parameter temperature dependent model for the collision diameter and well depth parameters of the Lennard-Jones potential energy model. Subsequently, vapor-liquid coexistence curves for argon, krypton, and methane were simulated using NVT Gibbs ensemble Monte Carlo (GEMC). The simulations were carried out using both temperature independent and temperature dependent parameters. The critical temperature and density were determined using the Ising-scaling model. The results using temperature dependent parameters produce, in general, more accurate phase diagrams compared to the diagrams generated using temperature independent interaction parameters. The root mean square deviation (RMSD) is reduced by 42.1% using temperature dependent interaction parameters for argon. Also, there was no significant difference between the results obtained using temperature dependent interaction parameters and the highly accurate and computationally demanding phase diagrams based on three body contributions.