THE EXTENDED NPT AND NVT PLUS TEST PARTIC LE METHODS FOR THE DETERMINATION OF VAPOR-LIQUID-EQUILIBRIA OF PURE FLUIDS

Two new simulation methods are suggested for the determination of vapo ur-liquid equilibria of pure molecular fluids. The extended NpT plus t est particle method is based on the third order Taylor series expansio n of the chemical potential with respect to beta = 1/kT and the pressu re. In the NVT plus test particle method the pressure and the chemical potential are expanded with respect to the number density and beta. T he coefficients of the series are determined an the basis of fluctuati on formulas. The chemical potential is calculated by the test particle method. Bath methods enable derivation of the equilibrium data in a c ertain temperature range from two (a gas- and a liquid-side) simulatio ns. The methods are tested on the Lennard-Jones fluid.