Mode Coupling and Dynamical Heterogeneity in Colloidal Gelation: A Simulation Study

TL;DR

This simulation study investigates the dynamics of colloidal gels near gelation, revealing a bimodal particle population and dynamic heterogeneity linked to structural differences, with implications for understanding glassy dynamics.

Contribution

It demonstrates the coexistence of mode coupling theory predictions with collective dynamic heterogeneity in colloidal gelation.

Findings

Quantitative agreement of MCT with correlator decay

Identification of bimodal fast and slow particle populations

Long exchange times indicating collective heterogeneity

Abstract

We present simulation results addressing the dynamics of a colloidal system with attractive interactions close to gelation. Our interaction also has a soft, long range repulsive barrier which suppresses liquid-gas type phase separation at long wavelengths. The new results presented here lend further weight to an intriguing picture emerging from our previous simulation work on the same system. Whereas mode coupling theory (MCT) offers quantitatively good results for the decay of correlators, closer inspection of the dynamics reveals a bimodal population of fast and slow particles with a very long exchange timescale. This population split represents a particular form of dynamic heterogeneity (DH). Although DH is usually associated with activated hopping and/or facilitated dynamics in glasses, the form of DH observed here may be more collective in character and associated with static (i.e., structural) heterogeneity.