Relationship between thermodynamics and dynamics of supercooled liquids

TL;DR

This paper explores the connection between thermodynamics and dynamics in supercooled liquids, showing that excess entropy can predict how diffusivity changes with supercooling, linking fluid behavior from gas to glass states.

Contribution

It provides the first evidence that excess entropy captures the effect of supercooling on diffusivity, unifying thermodynamic and dynamic descriptions of supercooled liquids.

Findings

Excess entropy correlates with diffusivity across supercooling.

Supercooling modifies diffusivity in a way predictable by excess entropy.

Thermodynamics and dynamics are linked through a single thermodynamic quantity.

Abstract

Diffusivity, a measure for how rapidly a fluid self-mixes, shows an intimate, but seemingly fragmented, connection to thermodynamics. On one hand, the "configurational" contribution to entropy (related to the number of mechanically-stable configurations that fluid molecules can adopt) has long been considered key for predicting supercooled liquid dynamics near the glass transition. On the other hand, the excess entropy (relative to ideal gas) provides a robust scaling for the diffusivity of fluids above the freezing point. Here we provide, to our knowledge, the first evidence that excess entropy also captures how supercooling a fluid modifies its diffusivity, suggesting that dynamics, from ideal gas to glass, is related to a single, standard thermodynamic quantity.