Dynamical heterogeneity in a glass forming ideal gas

TL;DR

This study investigates the dynamical heterogeneities in a model of ideal gas particles that exhibit glassy behavior, revealing that local environment influences particle mobility and that large dynamical length scales develop despite minimal clustering.

Contribution

It provides an extensive analysis of dynamical heterogeneities in a system with ideal gas structure but glass-like dynamics, highlighting the complexity of mobility and length scales.

Findings

Local environment influences particle diffusion propensity.

Large dynamical length scales develop at moderate densities.

Mobility measures may not fully capture dynamical length scales.

Abstract

We conduct a numerical study of the dynamical behavior of a system of three-dimensional crosses, particles that consist of three mutually perpendicular line segments rigidly joined at their midpoints. In an earlier study [W. van Ketel et al., Phys. Rev. Lett. 94, 135703 (2005)] we showed that this model has the structural properties of an ideal gas, yet the dynamical properties of a strong glass former. In the present paper we report an extensive study of the dynamical heterogeneities that appear in this system in the regime where glassy behavior sets in. On the one hand, we find that the propensity of a particle to diffuse is determined by the structure of its local environment. The local density around mobile particles is significantly less than the average density, but there is little clustering of mobile particles, and the clusters observed tend to be small. On the other hand, dynamical susceptibility results indicate that a large dynamical length scale develops even at moderate densities. This suggests that propensity and other mobility measures are an incomplete measure of dynamical length scales in this system.