Inherent structures and distribution functions for liquids that freeze into bcc crystals

Abstract

The collection of potential energy minima in a condensed phase determines its inherent packing structures. We have examined these inherent structures for a simple model substance which (like Na) freezes into a bcc crystal. Molecular dynamics trajectories at several different temperatures were periodically sampled, and each of the configurations was ‘‘quenched’’ by a steepest-descent construction into a nearby potential energy minimum. The resulting collections of inherent structures possess quenched pair correlation functions that are nearly independent of the initial-state temperature, provided the latter correspond to fluid states. Attempts to reconstitute the equilibrium pair correlation functions by thermally broadening the quenched versions, using harmonic Einstein or Debye vibrational approximations, were clear failures. Evidently the true broadening phenomenon entails substantial anharmonicity.