Adam-Gibbs model in the density scaling regime and its implications for the configurational entropy scaling

TL;DR

This paper extends the Adam-Gibbs model to include density scaling, linking structural relaxation times with configurational entropy in glass-forming materials, and demonstrates that both can be scaled using a common exponent.

Contribution

The study introduces a density scaling approach to the Adam-Gibbs model, establishing a direct relation between relaxation times and configurational entropy in the density scaling regime.

Findings

Structural relaxation times scale with configurational entropy.

The density scaling exponent relates relaxation dynamics to thermodynamics.

The model unifies temperature and volume effects in glass transition.

Abstract

To solve a long-standing problem of condensed matter physics with determining a proper description of the thermodynamic evolution of the time scale of molecular dynamics near the glass transition, we extend the well-known Adam-Gibbs model to describe the temperature-volume dependence of structural relaxation times, ${\tau}_{\alpha} (T,V)$. We employ the thermodynamic scaling idea reflected in the density scaling power law, ${\tau}_{\alpha}=f(T^{-1} V^{-\gamma } ) $, recently acknowledged as a valid unifying concept in the glass transition physics, to discriminate between physically relevant and irrelevant attempts at formulating the temperature-volume representations of the Adam-Gibbs model. As a consequence, we determine a straightforward relation between the structural relaxation time ${\tau}_{\alpha}$ and the configurational entropy $S_c$, giving evidence that also $S_c (T,V)=g(T^{-1} V^{-\gamma} )$ with the exponent {\gamma} that enables to scale ${\tau}_{\alpha} (T,V)$. This important finding has meaningful implications for the linkage between thermodynamics and molecular dynamics near the glass transition, because it implies that ${\tau}_{\alpha}$ can be scaled with $S_c$.