VAPOR-LIQUID-EQUILIBRIA OF LENNARD-JONES MODEL MIXTURES FROM THE NPT PLUS TEST PARTICLE METHOD

The NpT + test particle method for the calculation of vapour liquid ph ase equilibria (VLE) is applied to ten binary Lennard-Jones mixtures w hich were studied previously with the Gibbs ensemble (Harismiadis et a l., 1991). The present method uses one simulation for the description of the liquid. For the vapour two simulations are required at higher d ensities, whilst at lower vapour densities the Haar-Shenker-Kohler (HS K) equation of state is used. The chemical potentials from simulation are calculated by Widom's test particle insertion method (Widom, 1963) and adjusted with the results from the particle swap method, which yi elds the differences of the chemical potentials. Additionally, VLE res ults are obtained by using the Fischer-Lago-Bohn perturbation theory f or the liquid and the HSK equation for the vapour. A comparison of the new simulation results with those of the Gibbs ensemble shows qualita tive agreement but in most cases smaller error bars and considerably l ess scatter of the present data. Moreover, the simulations confirm the good to excellent performance of the perturbation theory.