The free energy of a liquid when viewed as a population of overlapping clusters

TL;DR

This paper explores how the free energy of a liquid can be understood through local clusters, highlighting the role of overlapping coordination shells in entropy and providing explicit formulas validated by simulations.

Contribution

It introduces an explicit decomposition of liquid free energy into local clusters and extends the Favoured Local Structure model to include spatial inhomogeneity.

Findings

Explicit expressions for structural energy and entropy derived

Comparison with simulation data validates the high-temperature approximation

Extension to inhomogeneous distributions considered

Abstract

The expression of the free energy of a liquid in terms of an explicit decomposition of the particle configurations into local coordination clusters is examined. We argue that the major contribution to the entropy associated with structural fluctuations arises from the local athermal constraints imposed by the overlap of adjacent coordination shells. In the context of the recently developed Favoured Local Structure model [Soft Matt. 11, 3322 (2015)], we derive explicit expressions for the structural energy and entropy in the high temperature limit, compare this approximation with simulation data and consider the extension of this free energy to the case of spatial inhomogeneity in the distribution of local structures.