Volume change on melting for systems with inverse-power-law interactions

We consider the change in volume on melting for systems interacting with a repulsive $r^{-n}$ potential. Using the scaling property for inverse-power-law systems and the Clausius-Clapeyron equation, we show that the change in volume on melting must go to zero as $n\to D$, the dimensionality of the system. For $n<~D$ finite excess thermodynamic properties can be defined by using a uniform neutralizing background. We produce a system with a uniform background as the limit of a classical two-component system and again find no change in volume on melting. Possible implications of these results for simulation studies of two-dimensional melting are discussed.