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

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.