Reliable Determination of the Liquid-Vapor Critical Point by theNVTPlus Test Particle Method

We find out that the N V T plus test particle method is effective to obtain the reliable data for 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 the undesirable volume fluctuations do not occur between the liquid and vapor phase. As a consequence it becomes possible to make the simulations stable even near the critical point. This is an outstanding advantage of the N V T plus test particle method when compared to the N p T plus test particle method. We apply the N V T plus test particle method to the Lennard-Jones 12–6 potential. We determine the coexistence curve far closer to the critical point than the result of the N p T plus test particle method. By applying the mixed-field finite-size scaling idea to our data, we obtain the critical temperature as T c * =1.3207(4), the critical density as ρ c * =0.316(1) and the critical pressure as p c * =0.1288(5). These values for T c * , ρ c * and p c * are the world-champion values since the error bars of these quantities are the smallest among those obtained so far.