Structure of the liquid–vapor interface of a metal from a simple model potential: Corresponding states of the alkali metals

Abstract

We present the results of self-consistent quantum Monte Carlo simulations of the structures of the liquid-vapor interfaces of alkali metals (Na, K, Rb, Cs) using a modified semiempirical empty-core model potential. The purpose of this investigation is to simplify the analysis of inhomogeneous metals sufficiently to permit qualitative inferences to be drawn about the properties of families of metals. Both electronic and ion density profiles along the normal to the surface show oscillations in the liquid–vapor transition zone. These oscillations closely resemble those found in previous simulation studies of the liquid–vapor interfaces of alkalis, based on sophisticated nonlocal model potentials. Because of its semianalytical representation, the model potential used in this paper allows considerable simplification in the computational scheme relative to the effort involved in the previously published simulations. We find liquid Na, K, Rb, and Cs to exhibit similar surface layering. Moreover, our results suggest the existence of a corresponding states representation of the properties of this class of metals. We expect this new analysis will be useful in predicting the qualitative properties of the surface structures of a broad range of pure liquid metals.