Excess Thermodynamic Properties of Ternary Fluid Mixtures from Molecular Dynamics Simulation and Van Der Waals One-Fluid Theory

Abstract

In this paper, we report isothermal–isobaric molecular dynamics simulation results for total and excess thermodynamic properties of three selected nonideal ternary fluid mixtures, in which particles interact via a Lennard-Jones pair potential. In these mixtures, size parameters of the components are kept to be the same, but energy parameters of the components differ significantly. Simulation results are reported for mixture density, internal energy, excess Gibbs free energy, excess volume and excess enthalpy of equimolar ternary mixtures as a function of temperature and pressure. The excess Gibbs free energy is obtained directly using the coupling parameter charging approach, which avoids the cancellation or magnification of errors in the simulation. These simulation results are used to check the accuracy of a form of the van der Waals one–fluid theory, which uses an accurate equation of state for the pure fluids. Van der Waals one–fluid theory is successful in predicting total and excess properties of these nonideal mixtures within simulation uncertainties.

Key Words:

• Computer simulation
• excess thermodynamic properties
• ternary fluid mixtures
• van der Waals one–fluid theory