Localised soft modes and the supercooled liquid's irreversible passage through its configuration space

TL;DR

This study uses simulations to link localized low-frequency normal modes in supercooled liquids to irreversible particle rearrangements, revealing how soft modes influence heterogeneity and anisotropic relaxation behaviors.

Contribution

It identifies a strong correlation between localized soft modes and irreversible structural reorganization, highlighting their role in dynamic heterogeneity.

Findings

Localized soft modes predict particle rearrangements.

Spatial distribution of soft modes persists despite reorganization.

Soft modes cause anisotropic particle displacements during beta relaxation.

Abstract

Using computer simulations, we show that the localized low frequency normal modes of a configuration in a supercooled liquid are strongly correlated with the irreversible structural reorganization of the particles within that configuration. Establishing this correlation constitutes the identification of the aspect of a configuration that determines the heterogeneity of the subsequent motion. We demonstrate that the spatial distribution of the summation over the soft local modes can persist in spite of particle reorganization that produces significant changes in individual modes. Along with spatial localization, the persistent influence of soft modes in particle relaxation results in anisotropy in the displacements of mobile particles over the timescale referred to as beta relaxation.