Inherent structure theory of liquids in the hard-sphere limit

Abstract

Atomic pair correlation functions for liquids provide an image of temperature-dependent short-range order. If the thermal ensemble of atomic configurations is mapped (by steepest descent on the potential hypersurface) onto potential energy minima, the pair correlation function from the resulting transformed configurations exhibits substantial image enhancement, revealing short-range order in a much more vivid fashion. Previous studies of model atomic liquids have demonstrated that at fixed density, mapped short-range order is virtually independent of the initial temperature, and thereby amounts to an ‘‘inherent structure’’ for the liquid. The present paper investigates steepest-descent mapping and inherent structure for hard spheres, construed as the infinite-n limit for pair potentials (a/r)n. Methods used are both analytical and simulational, the latter involving molecular dynamics for n=12 and 24. Results show that inherent structures in the hard-sphere limit are randomly packed configurations, where particle radii have been inflated to the point of jamming.