Improving the efficiency of a new infinite order perturbation method to simulate surface forces

Svensson and Woodward [1] have recently developed an infinite order thermodynamic perturbation technique, utilizing free energy differences, with which surface forces and free energies may be simulated without particle insertions. In this Note, we investigate another free energy difference method, in which we employ an isotension ensemble version of the variance minimization scheme, introduced by Bennet [2] for canonical systems. It is shown that this method provides a substantially improved efficiency, as compared with the simple thermodynamic perturbation technique. The applicability is also increased, since fluids with hard cores may be treated without restrictions.