Generalized Mode-Coupling Theory for Mixtures of Brownian Particles

TL;DR

This paper extends generalized mode-coupling theory (GMCT) to colloidal mixtures with Brownian dynamics, providing a hierarchical framework that improves predictions of glassy dynamics and confirms its consistency with Newtonian GMCT.

Contribution

The paper derives a fully generalized GMCT for Brownian particles, establishing a hierarchy of equations and demonstrating its equivalence to Newtonian GMCT in the overdamped limit.

Findings

Hierarchical equations for Brownian GMCT are derived and validated.

Brownian GMCT reduces to Newtonian GMCT in the overdamped limit.

Applying the theory to a binary Lennard-Jones mixture shows improved predictive accuracy.

Abstract

Generalized mode-coupling theory (GMCT) has recently emerged as a promising first-principles theory to study the poorly understood dynamics of glass-forming materials. Formulated as a hierarchical extension of standard mode-coupling theory (MCT), it is able to systematically improve its predictions by including the exact dynamics of higher-order correlation functions into its hierarchy. However, in contrast to Newtonian dynamics, a fully generalized version of the theory based on Brownian dynamics is still lacking. To close this gap, we provide a detailed derivation of GMCT for colloidal mixtures obeying a many-body Smoluchowski equation. We demonstrate that a hierarchy of coupled equations can again be established and show that these, consistent with standard MCT, are identical to the ones obtained from Newtonian GMCT when taking the overdamped limit. Consequently, the non-trivial similarity between Brownian and Newtonian MCT is maintained for our newly developed multi-component GMCT. As a proof of principle, we also solve the generalized mode-coupling equations for the binary Kob-Andersen Lennard-Jones mixture undergoing Brownian dynamics, and confirm the improved predictive power of the theory upon using more levels of the GMCT hierarchy of equations.