Monte Carlo intrinsic surfaces and density profiles for liquid surfaces

Operational definitions for the intrinsic surface to be used in computer simulations of liquid surfaces are discussed and tested along with Monte Carlo simulations of simple liquid models. The results are contrasted with the theoretical framework of the capillary wave theory (CWT), and with the strongly structured intrinsic profiles used in the interpretation of x-ray reflectivity experiments for cold liquid metals. The definition of a minimal area intrinsic surface pinned to a set of pivot atoms at the surface leads to intrinsic density profiles with the sharpest atomic resolution, but which are beyond the assumption of the CWT, with strong correlations between the intrinsic profiles and the fluctuations of the intrinsic surface and with an effective wave-vector-dependent surface tension.