Structural signatures of mobility on intermediate time scales in a supercooled fluid

TL;DR

This study uses computer simulations to analyze how particle displacements in supercooled fluids relate to their structural environment on intermediate time scales, revealing correlations between immobility and local structure.

Contribution

It demonstrates that immobile particles show stronger structural correlations than mobile ones, highlighting the link between structure and dynamics in supercooled fluids.

Findings

Immobile particles have stronger pair correlations than mobile particles.

The displacement distribution shows bifurcation into immobile and mobile subpopulations.

Structural-dynamic correlations depend on observation time.

Abstract

We use computer simulations to explore the manner in which the particle displacements on intermediate time scales in supercooled fluids correlate to their dynamic structural environment. The fluid we study, a binary mixture of hard spheres, exhibits classic signatures of dynamic heterogeneity, including a bifurcated single-particle displacement distribution (i.e., subpopulations of immobile and mobile particles). We find that immobile particles, during the course of their displacements, exhibit stronger average pair correlations to their neighbors than mobile particles, but not necessarily higher average coordination numbers. We discuss how the correlation between structure and single-particle dynamics depends on observation time.