Motility-induced phase separation of soft active Brownian particles

Abstract

Motility-induced phase separation (MIPS) is the hallmark of non-equilibrium phase transition in active matter. Here, by means of Brownian dynamics simulations, we determine the phase behavior and the critical point for phase separation induced by motility of a two-dimensional system of soft active Brownian particles, whose interaction is modeled by the generalized purely repulsive Weeks–Chandler–Andersen potential. We refer to this model as soft active Brownian particles. We determine and analyze the influence of particle softness on the MIPS and show that the liquid–gas coexistence region is wider, the softer the interparticle interactions becomes. Moreover, the critical value of the self-propulsion velocity at which diluted and dense phases start to coexist also increases; as a consequence, the softer the particle interaction is, the bigger self-propulsion velocities are needed in order to observe a MIPS.

A passive star polymer in a dense active bath: insights from computer simulations

“…For instance, increasing the softness of colloidal particles tends to shift critical values towards higher ranges. 55,62–66 In addition to these discussions, the inclusion of torque in ABPs, as well as topological constraints such as connecting them in a ring, also disrupts conventional MIPS, instead exhibiting micro-phase separation. 65,67…”