Heterogeneities in the Glassy State

TL;DR

This study uses molecular dynamics simulations to analyze heterogeneities in a glassy binary Lennard-Jones system, revealing temperature-dependent clustering behaviors of mobile and immobile particles and their vibrational properties.

Contribution

It provides new insights into the temperature-dependent clustering and vibrational amplitude distributions of particles in the glassy state, supported by comparison with mean field theory.

Findings

Immobile particles cluster more at higher temperatures, blocking each other.

Mobile particles form more pronounced clusters at low temperatures.

Vibrational amplitude distribution follows scaling near the glass transition.

Abstract

We study heterogeneities in a binary Lennard-Jones system below the glass transition using molecular dynamics simulations. We identify mobile and immobile particles and measure their distribution of vibrational amplitudes. For temperatures near the glass transition the distribution of vibrational amplitudes obeys scaling and compares reasonably well with a mean field theory for the amorphous solid state. To investigate correlations among the immobile and mobile particles we identify clusters and analyze their size and shape. For a fixed number of immobile particles we observe that the immobile particles cluster more strongly together as the temperature is increased which allows the particles to block each other more effectively, and to therefore stay immobile. For the mobile particles, on the other hand, the clustering is most pronounced at small temperatures, indicating that mobility at low temperatures can only be sustained in cooperative motion.