Non-Equilibrium Thermodynamic Description of the Coupling between Structural and Entropic Modes in Supercooled Liquids

TL;DR

This paper develops a non-equilibrium thermodynamic model to describe the coupling between structural and entropic modes in supercooled liquids, explaining experimental observations of thermal and structural relaxation behaviors.

Contribution

A novel non-equilibrium thermodynamic model that captures the interaction between structural and entropic modes in supercooled liquids.

Findings

The model reproduces experimental data on glycerol's density response.

It explains the dip in thermal conductivity and flattening of alpha-relaxation time.

The approach links thermodynamics with dynamic relaxation phenomena.

Abstract

The density response of supercooled glycerol to an impulsive stimulated thermal grating (q=0.63 micron^-1) has been studied in the temperature range (T=200-340 K) where the structure rearrangement (alpha-relaxation) and thermal diffusion occur on the same time scale. A strong interaction between the two modes occurs giving rise to a dip in the T-dependence of the apparent thermal conductivity and a flattening of the apparent alpha-relaxation time upon cooling. A non-equilibrium thermodynamic (NET) model for the long time response of relaxing fluids has been developed. The model is capable to reproduce the experimental data and to explain the observed phenomenology.