Statistical mechanical approach to secondary processes and structural relaxation in glasses and glass formers

TL;DR

This paper models the complex relaxation dynamics in glasses and liquids, revealing how different relaxation processes interact and predicting their behavior above the dynamic arrest temperature using a mean-field approach and Mode Coupling Theory.

Contribution

It introduces a model capturing two distinct time-scale bifurcations in glassy dynamics and compares mean-field predictions with Mode Coupling Theory results.

Findings

The model predicts a clear separation of relaxation peaks.

It reproduces excess wing structures in susceptibility loss.

Predictions align with Mode Coupling Theory outcomes.

Abstract

The interrelation of dynamic processes active on separated time-scales in glasses and viscous liquids is investigated using a model displaying two time-scale bifurcations both between fast and secondary relaxation and between secondary and structural relaxation. The study of the dynamics allows for predictions on the system relaxation above the temperature of dynamic arrest in the mean-field approximation, that are compared with the outcomes of the equations of motion directly derived within the Mode Coupling Theory (MCT) for under-cooled viscous liquids. Varying the external thermodynamic parameters a wide range of phenomenology can be represented, from a very clear separation of structural and secondary peak in the susceptibility loss to excess wing structures.