Anti-Swarming: Structure and Dynamics of Repulsive Chemically Active Particles

TL;DR

This paper investigates the structure and dynamics of chemically active particles that repel each other via diffusiophoretic interactions, revealing conditions for crystal formation and phase transitions in confined systems.

Contribution

It introduces a framework linking diffusiophoretic interactions to electrostatic plasma models, and characterizes the crystallization behavior of active particles under strong repulsion.

Findings

BCC crystals form when repulsion overcomes Brownian motion

FCC crystals can also be stable under certain conditions

Liquid-to-crystal transition occurs at a coupling parameter of about 140

Abstract

Chemically active Brownian particles with surface catalytic reactions may repel each other due to diffusiophoretic interactions in the reaction and product concentration fields. The system behavior can be described by a `chemical' coupling parameter $\Gamma_c$ that compares the strength of diffusiophoretic repulsion to Brownian motion, and by a mapping to the classical electrostatic One Component Plasma (OCP) system. When confined to a constant-volume domain, Body-Centered Cubic crystals spontaneously form from random initial configurations when the repulsion is strong enough to overcome Brownian motion. Face-Centered Cubic crystals may also be stable. The `melting point' of the `liquid-to-crystal transition' occurs at $\Gamma_c\approx140$ for both BCC and FCC lattices.