An inherent structure view of liquid-vapor interfaces

The formal statistical mechanical theory describing liquid-vapor interfaces at thermal equilibrium has been incomplete, owing partly to discrepancies between two primary views, the local free energy approach originated by van der Waals and the capillary wave approach initiated by Mandelstam. The former provides detailed prescriptions for interfacial density profiles and surface tensions, and has recently been tailored to conform to nonclassical critical phenomena. The latter postulates a crude discontinuous density profile that is geometrically delocalized by surface excitations, but which qualitatively incorporates basic gravitational effects that are missing in the van der Waals method. The present analysis provides a formalism within which both approaches can be reconciled. It draws upon the inherent structure mapping procedure to define an intrinsic liquid-vapor density profile which invokes no arbitrary parameters that are not already present in the many-particle potential energy function or its thermodynamics. By construction, this intrinsic profile plays a role conventionally given to a van der Waals interface profile, and although it is free of capillary waves it can serve as a starting point for evaluating the gravitational implications of those interfacial fluctuation effects.