A new simulation method for the determination of the vapour-liquid equilibria in the grand canonical ensemble

A new simulation method is introduced for the determination of the vapour-liquid phase separation of pure fluids in the grand canonical ensemble. It is based on the third-order Taylor series of the pressure with respect to the reciprocal temperature term (β = 1/kT) and the configurational chemical potential. The coefficients of the series can be obtained via fluctuation formulae by performing grand canonical Monte Carlo simulations at suitably prescribed vapour- and liquid-phase raw points. The method was tested on the Lennard-Jones fluid. Though there is some inefficiency in the calculation of the pressure on the liquid side, the algorithm enables the derivation of the equilibrium data with satisfactory accuracy.