Total and excess properties of nonideal ternary fluid mixtures via isothermal-isobaric molecular dynamics simulation: size and energy parameter effects

Abstract

We report isothermal-isobaric molecular dynamics simulation results for total and excess properties of 162 ternary mixtures of Lennard-Jones fluids. Simulations were performed at energy and size parameter ratios in the range ( 1 ≤ ϵ CC ϵ AA ≤ 2 ; 1 ≤ σ CC σ AA ≤ 2 ). In these mixtures, the component A consists of the smallest atoms, while the component C consists of the biggest atoms. The energy and size parameter ratios of the component B lie in the range ( 1 ≤ ϵ BB ϵ AA ≤ 1.75 ; 1 ≤ σ BB σ AA ≤ 1.75 ). Results are reported for mixture density, residual internal energy, excess enthalpy and excess volume of 120 equimolar mixtures and 42 nonequimolar mixtures at 5 different thermodynamic conditions: ( kT ϵ AA = 1 , Pσ AA 3 ϵ AA = 0.5 ); ( kT ϵ AA = 1.5 , Pσ AA 3 ϵ AA = 1.5 ); ( kT ϵ AA = 2 , Pσ AA 3 ϵ AA = 1.2 ); ( kT ϵ AA = 2 , Pσ AA 3 ϵ AA = 2.5 ) and ( kT ϵ AA = 3 , Pσ AA 3 ϵ AA = 2.5 ). Some of these simulation results are used to test the accuracy of the recently developed statistical mechanical perturbation theory and van der Waals one-fluid theory of ternary mixtures. Perturbation theory is very successful in describing simulation results of highly nonideal mixtures, while van der Waals one-fluid theory can describe moderately nonideal mixtures only.