Competing Relaxation Channels in Continuously Polydisperse Fluids: A Mode-Coupling Study

TL;DR

This study uses Mode-Coupling Theory to analyze how high size polydispersity in fluids influences glass transition, revealing stabilization effects, localization length separation, and the importance of smallest particles in relaxation dynamics.

Contribution

It provides a systematic MCT analysis of continuously polydisperse fluids, highlighting the role of polydispersity shape and particle size in glassy dynamics and heterogeneities.

Findings

High polydispersity stabilizes the liquid phase against vitrification.

Separation of localization lengths between smallest and largest particles.

Smallest particles play a key role in structural relaxation.

Abstract

Systems with a high degree of size polydispersity are becoming standard in the computational study of deeply supercooled liquids. In this work we perform a systematic analysis of continuously polydisperse fluids as a function of the degree of polydispersity within the framework of the Mode-Coupling Theory of the glass transition (MCT). Our results show that a high degree of polydispersity tends to stabilize the liquid phase against vitrification, the magnitude of which depends on the shape of the polydispersity distribution. Further, we report on a separation between the localization lengths of the smallest and largest particles. A diameter-resolved analysis of the intermediate scattering functions reveals that this separation significantly stretches the relaxation patterns, which we quantitatively study by an analysis of the dynamical exponents predicted by the theory. Our observations have strong implications for our understanding of the nature of dynamical heterogeneities and localization lengths in continuously polydisperse systems. These results suggest that the dynamics of the smallest particles is of central importance to understand structural relaxation of continuously size polydisperse fluids, already in the mildly supercooled regime where MCT is usually applicable.