Calculation of excess free energy from the averaged effective acceptance ratio for the Lennard-Jones fluid and the inverse twelve fluid

The method of calculating the excess Helmholtz free energy from the averaged effective acceptance ratio is applied to the Lennard-Jones fluid and the inverse twelve fluid. The excess entropy is calculated directly from the average of the effective acceptance ratio through the Metropolis Monte Carlo simulation. This method does not need any reference system. This method is easy to implement. This method is an efficient method for calculating the free energy. The results of this method were satisfactory compared with other methods. This method can be applied directly to molecular dynamics simulation.