Democratic particle motion for meta-basin transitions in simple glass-formers

TL;DR

This study uses molecular dynamics simulations to analyze particle motions in supercooled liquids, revealing that alpha-relaxation involves rapid, collective cluster transitions between meta-basins, supporting the concept of cooperatively rearranging regions.

Contribution

It introduces a new analysis based on the distance matrix to identify collective particle clusters involved in meta-basin transitions in glass-formers.

Findings

Alpha-relaxation corresponds to rapid crossings between meta-basins.

Transitions involve collective motion of about 40 particles.

String-like motions are not significant in these transitions.

Abstract

We use molecular dynamics computer simulations to investigate the local motion of the particles in a supercooled simple liquid. Using the concept of the distance matrix we find that the alpha-relaxation corresponds to a small number of crossings from one meta-basin to a neighboring one. Each crossing is very rapid and involves the collective motion of O(40) particles that form a relatively compact cluster, whereas string-like motions seem not to be relevant for these transitions. These compact clusters are thus candidates for the cooperatively rearranging regions proposed long times ago by Adam and Gibbs.