Vapour-liquid equilibria of dipolar two-centre Lennard-Jones fluids from a physically based equation of state and computer simulations

The paper is concerned with the model fluid consisting of two-centre Lennard-Jones molecules with embedded axial dipole moment (2CLJD), particularly with its vapour-liquid phase equilibrium behaviour as calculated from different molecular simulation methods and from an analytical equation of state. The focus of the present study is the parameter region of large elongations (L in the range from 0.505 to 1.0) and large dipole moments (mu(*2) in the range from 9 to 12) of the 2CLJD fluid. In order to assess the performance of independent molecular simulation methods and to examine the validity of a physically based equation of state of the augmented van der Waals type within this parametric region, we have calculated the 2CLJD model fluid properties along the vapour-liquid coexistence locus by the Gibbs ensemble Monte Carlo method, Gibbs-Duhem integration technique looking at the effect of different starting state points, the NpT plus test particle method, and from the equation of state. Within the entire region examined, fairly good mutual agreement of the independent simulation methods is observed. The equation of state represents a good compromise between the results of different simulation methods at intermediate elongations but fails at large elongations. The extended base of pseudoexperimental data is prerequisite for further equation of state development.