Precise determination of the liquid–vapor critical point by the NVT plus test particle method

Abstract

We find that the NVT plus test particle method is effective in obtaining reliable data on the liquid–vapor critical point from microscopic information of interatomic potentials. The basic idea of this method is to calculate chemical potentials by test particle insertions during canonical simulations, from which the equilibrium vapor pressure is determined. Simulations are performed at a fixed volume so that undesirable volume fluctuations do not occur. As a consequence, it becomes possible to make the simulations stable even near the critical point. This is an outstanding advantage of the NVT plus test particle method when compared to the NpT plus test particle method. We apply the NVT plus test particle method to the Lennard-Jones 12-6 potential. We obtain the best values of the critical point to date since the error bars of these quantities are the smallest among those obtained so far.