Nucleation pathway and kinetics of phase-separating active Brownian particles

TL;DR

This paper investigates how active Brownian particles undergo phase separation, revealing that their nucleation pathways and kinetics resemble passive systems, with detailed insights into transition states involving cluster size and particle polarization.

Contribution

The study demonstrates that active Brownian particles exhibit phase separation kinetics similar to passive systems and identifies key microscopic features of the transition states.

Findings

Nucleation rate behavior mirrors passive liquid-vapor separation.

Transition states involve cluster size and radial polarization.

Effective free energy scenario extends to kinetics.

Abstract

Suspensions of purely repulsive but self-propelled Brownian particles might undergo phase separation, a phenomenon that strongly resembles the phase separation of passive particles with attractions. Here we employ computer simulations to study the nucleation kinetics and the microscopic pathway active Brownian disks take in two dimensions when quenched from the homogeneous suspension to propulsion speeds beyond the binodal. We find the same qualitative behavior for the nucleation rate as a function of density as for a passive suspension undergoing liquid-vapor separation, suggesting that the scenario of an effective free energy also extends to the kinetics of phase separation. We study the transition in more detail through a committor analysis and find that transition states are best described by a combination of cluster size and the radial polarization of particles in the cluster.