Thermodynamic properties of mixtures with linear molecules from WCA-type perturbation theory in comparison with MD results

Abstract

Mixtures of Lennard-Jones (LJ) with two-centre Lennard-Jones (2CLJ) molecules are considered. The 2CLJ molecules have successively increasing elongations with parameters ϵ and σ chosen such that the saturated liquid density and the vapour pressure of the pure components remain the same. At a liquid state point given by T and p = 0 the volumes and the enthalpies of the pure components and of the equimolar mixtures are calculated from our WCA-type perturbation theory (PT) and compared to MD-NpT simulation results. It is found that for elongations up to L = 0·505, the volumes and enthalpies agree within some tenths of one per cent. For larger elongations, however, the enthalpies especially show larger differences as had to be expected. The excess properties from PT agree again quite well with those from MD up to L = 0·505 and show qualitatively the right behaviour for larger elongations.