The free energy of the metastable supersaturated vapor via restricted ensemble simulations

Abstract

Pressure, excess chemical potential, and excess free energy, with respect to ideal gas data at different densities of the supersaturated Lennard-Jones particle vapor at the reduced temperature 0.7 are obtained by the restricted canonical ensemble Monte Carlo simulation method [D. S. Corti and P. Debenedetti, Chem. Eng. Sci. 49, 2717 (1994)]. The excess free energy values depend upon the constraints imposed on the system with local minima exhibited for densities below the spinodal density and monotonic variation for densities larger than the spinodal density. The results are compared with a molecular dynamics simulation study [A. Linharton et al., J. Chem. Phys. 122, 144506 (2005)] on the same system. The current study verifies the conclusion drawn by the simulation work that clustering of Lennard-Jones atoms exists even in the vicinity of spinodal. Our method gives an alternative to molecular dynamic simulations for the determination of equilibrium properties of a metastable fluid, especially close to the spinodal, and does not require a very large system to carry out the simulation.