Configurational entropy of polar glass formers and the effect of electric field on glass transition

TL;DR

This paper develops a theoretical model for polar liquids that explains configurational entropy, predicts effects of electric fields on glass transition, and aligns well with experimental thermodynamic data of molecular glass formers.

Contribution

It introduces a novel model based on Padé-perturbation expansions that captures configurational entropy and electric field effects on glass transition in polar liquids.

Findings

The model predicts an ideal glass transition with vanishing configurational entropy.

Electric fields raise the glass transition temperature, scaling quadratically with field strength.

The theory aligns with experimental thermodynamic data for molecular glass formers.

Abstract

A model of low-temperature polar liquids is constructed that accounts for configurational heat capacity, entropy, and the effect of a strong electric field on the glass transition. The model is based on Pad{\'e}-truncated perturbation expansions of the liquid state theory. Depending on parameters, it accommodates an ideal glass transition of vanishing configurational entropy and its avoidance, with a square-root divergent enumeration function at the point of its termination. A composite density-temperature parameter $\rho^\gamma/T$, often used to represent combined pressure and temperature data, follows from the model. The theory is in good agreement with experimental data for excess (over the crystal state) thermodynamics of molecular glass formers. We suggest that the Kauzmann entropy crisis might be a signature of vanishing configurational entropy of a subset of degrees of freedom, multipolar rotations in our model. This scenario has observable consequences: (i) a dynamical cross-over of the relaxation time and (ii) the fragility index defined by the ratio of the excess heat capacity and excess entropy at the glass transition. The Kauzmann temperature of vanishing configurational entropy, and the corresponding glass transition temperature, shift upward when the electric field is applied. The temperature shift scales quadratically with the field strength.