Calculation of excess free energy from averaged acceptance ratio in Monte Carlo simulation for hard sphere and hard dumbbell fluids

Abstract

The method of calculating the excess free enegy from the radial free space distribution function in the Monte Carlo simulation of the hard sphere system is modified and extended to the hard dumbbell system. The excess free energy is calculated from the average of the acceptance ratio at long distances. The excess free energy is also calculated from the average of the acceptance ratio in a cell with fixed volume. Calculations are performed for hard spheres and hard dumbbells with elongations l/σ from 0·2 to 1·0. The calculated results give good agreement compared with those of thermodynamic integration from the analytical equations of state.