Thermodynamic properties and structure of supercritical Stockmayer/Lennard-Jones fluid mixtures

Monte Carlo simulation has been used to obtain excess potential energies, Helmholtz energies of mixing, local concentration ratios and cluster size distribution of StockmayerLennard-Jones (STLJ) fluid mixtures as a simple model of polar-nonpolar fluid mixtures at three state points including the supercritical state. The results of the calculations for the Helmholtz energy of mixing show that the ST(μ∗2 = 4)LJ mixture will become immiscible in the region about xST = 0.333 at T∗ = 1.15, ϱ∗ = 0.822. Also, the asymmetric behaviors of UE∗ with respect to the ST composition are explained in terms of the ‘difficulties in breaking ST clusters’ and ‘orientational frustration relaxation’.