# Interparticle torques suppress motility-induced phase separation for rodlike particles

## TL;DR

This study investigates how interparticle torques influence motility-induced phase separation (MIPS) in self-propelled particles, revealing that elongated shapes suppress MIPS through collision dynamics, with implications for understanding active matter behavior.

## Contribution

The paper introduces a comprehensive simulation and analysis of MIPS suppression in rodlike particles, highlighting the role of particle shape and collision duration in phase behavior.

## Key findings

- Elongated particles suppress MIPS compared to isotropic particles.
- A collision duration-based mechanism explains MIPS suppression in rods.
- The suppression mechanism also accounts for MIPS enhancement in Vicsek-like particles.

## Abstract

To study the role of torque in motility-induced phase separation (MIPS), we simulate a system of self-propelled particles whose shape varies smoothly from isotropic (disks/spheres) to weakly elongated (rods). We construct the phase diagrams of 2D active disks, 3D active spheres and 2D/3D active rods of aspect ratio $l/\sigma=2$. A stability analysis of the homogeneous isotropic phase allows us to predict the onset of MIPS based on the effective swimming speed and rotational diffusion of the particles. Both methods find suppression of MIPS as the particle shape is elongated. We propose a suppression mechanism based on the duration of collisions, and argue that this mechanism can explain both the suppression of MIPS found here for rodlike particles and the enhancement of MIPS found for particles with Vicsek interactions.