From Liquid Structure to Configurational Entropy: Introducing Structural Covariance

TL;DR

This paper links the configurational entropy of liquids to their local structural geometries using a high-temperature expansion, revealing how structural covariance influences entropy and glass formation.

Contribution

It introduces a novel formalism connecting local structural covariance to configurational entropy, applicable to predicting glass-forming ability in lattice models.

Findings

Covariance predicts glass-forming ability.

Structural overlap controls entropy decrease.

Formalism applies to Favored Local Structure models.

Abstract

We connect the configurational entropy of a liquid to the geometrical properties of its local energy landscape, using a high-temperature expansion. It is proposed that correlations between local structures arises from their overlap and, being geometrical in nature, can be usefully determined using the inherent structures of high temperature liquids. We show quantitatively how the high-temperature covariance of these local structural fluctuations arising from their geometrical overlap, combined with their energetic stability, control the decrease of entropy with decreasing energy. We apply this formalism to a family of Favoured Local Structure (FLS) lattice models with two low symmetry FLS's which are found to either crystallize or form a glass on cooling. The covariance, crystal energy and estimated freezing temperature are tested as possible predictors of glass-forming ability in the model system.