Origin and Detection of Microstructural Clustering in Fluids with Spatial-Range Competitive Interactions

TL;DR

This paper investigates how fluids with competing interactions form microstructural clusters, using simulations and theory to link structure factors to cluster formation and distinguish between amorphous and crystalline clusters.

Contribution

It introduces a method to detect cluster formation from the static structure factor and clarifies the conditions under which microstructural clustering occurs in such fluids.

Findings

Clusters form when the correlation length exceeds the interaction lengthscale.

Distinct dynamics observed between amorphous and crystalline clusters.

Links established between structure factor features and phase behavior.

Abstract

Fluids with competing short-range attractions and long-range repulsions mimic dispersions of charge-stabilized colloids that can display equilibrium structures with intermediate range order (IRO), including particle clusters. Using simulations and analytical theory, we demonstrate how to detect cluster formation in such systems from the static structure factor and elucidate links to macrophase separation in purely attractive reference fluids. We find that clusters emerge when the thermal correlation length encoded in the IRO peak of the structure factor exceeds the characteristic lengthscale of interparticle repulsions. We also identify qualitative differences between the dynamics of systems that form amorphous versus micro-crystalline clusters.