Description:
A general statistical mechanical expression is derived for the surface tension of a fluid with an arbitrary many body interaction potential, which reduces to the Kirkwood–Buff formula under the assumption of pairwise additivity. Sum rules for the inhomogeneous system with the many body potential are also presented. These are then used to show that the general expression for surface tension is formally equivalent to the fluctuation formula due to Yvon, and to a recent correlation function expression of Jhon, Desai, and Dahler.