Self diffusion of reversibly aggregating spheres

TL;DR

This study simulates reversible cluster aggregation of hard spheres to understand how attraction strength and crowding influence self diffusion, revealing that diffusion slowdown is decoupled from cluster formation and gels only form at infinite attraction.

Contribution

It provides a detailed analysis of self diffusion in reversible aggregating spheres, showing how attraction strength affects diffusion independently of crowding and cluster formation.

Findings

Diffusion coefficient decreases with increasing attraction strength.

Diffusion becomes zero only at infinite attraction strength.

Attractive glasses are not formed at finite interaction strengths.

Abstract

Reversible diffusion limited cluster aggregation of hard spheres with rigid bonds was simulated and the self diffusion coefficient was determined for equilibrated systems. The effect of increasing attraction strength was determined for systems at different volume fractions and different interaction ranges. It was found that the slowing down of the diffusion coefficient due to crowding is decoupled from that due to cluster formation. The diffusion coefficient could be calculated from the cluster size distribution and became zero only at infinite attraction strength when permanent gels are formed. It is concluded that so-called attractive glasses are not formed at finite interaction strength.