Positive Tolman Length in a Lattice Gas with Three-Body Interactions

We present a new method to determine the curvature dependence of the interface tension between coexisting phases in a finite volume from free energies obtained by Monte Carlo simulations. For the example of a lattice gas on a 3D fcc lattice with nearest neighbor three-body interactions, we demonstrate how to calculate the equimolar radius R(e) as well as the radius R(s) of the surface of tension and thus the Tolman length delta(R(s)) = R(e) - R(s). Within the physically relevant range of radii, delta(R(s)) shows a pronounced R(s) dependence, such that the simple Tolman parametrization for the interface tension is refutable. For the present model, extrapolation of delta(R(s)) to R(s) -> infinity by various methods clearly indicates a positive limiting value.