Comparison of equations of state for pure Lennard–Jones fluids and mixtures with molecular simulation data

Several equations of state for Lennard–Jones (LJ) fluids and mixtures are used in this work, including Cotterman’s expresssion and SAFT-VR. A new set of coefficients for Cotterman equation is re-regressed by fitting both the reduced pressure and internal energy data from molecular simulations. Comparisons between the two sets of coefficients are carried out. The SAFT-VR EOS for LJ fluids and its simplified form by mean-field approximation are compared with the Cotterman EOS. Based on SAFT, the contribution due to the formation of chains is expressed as a function of background correlation function for reference fluid. Two reference fluids (the hard sphere and the LJ fluid) and three methods to calculate the background correlation function are adopted. The EOS is extended to mixtures by use of the van der Waals one-fluid (VDW1) mixing rules. Comparisons for the pressures and residual chemical potentials with molecular simulation data are reported. The accuracy of predictions for liquid–liquid equilibria (LLE) of binary LJ mixtures is also examined.