Monte Carlo calculation of the free energy for a dense fluid

Abstract

A simple and direct approach to the free energy of a dense simple fluid away from critical point is considered. Standard Monte Carlo sampling of free energy difference relative to a reference system for a range of model system sizes is employed. By using a range of a small number of particles, multi-stage samplings can be avoided and exponential extrapolation to the thermodynamic limit is assured in the absence of nearby critical point. The technique is demonstrated for the dense fluid interacting with the r-12 repulsive potential in three dimensions. The hard-sphere fluid reference system is used. The free energy estimate is in excellent agreement with published results from standard thermodynamic integration of the equation of state obtained from Monte Carlo simulation.