Isotropic-nematic transition of self-propelled rods in three dimensions

TL;DR

This study uses simulations to explore how self-propelled rods in three dimensions undergo an isotropic-nematic transition, revealing that activity shifts the phase boundary to higher densities and that this behavior is robust across system sizes.

Contribution

It demonstrates that activity influences the isotropic-nematic transition in 3D self-propelled rods, a feature consistent across different models and system sizes.

Findings

Activity shifts the phase boundary to higher densities.

The active IN phase boundary is distinct from polar-cluster boundaries.

The phase boundary is not sensitive to system size.

Abstract

Using overdamped Brownian dynamics simulations we investigate the isotropic-nematic (IN) transition of self-propelled rods in three spatial dimensions. For two well-known model systems (Gay-Berne potential and hard spherocylinders) we find that turning on activity moves to higher densities the phase boundary separating an isotropic phase from a (nonpolar) nematic phase. This active IN phase boundary is distinct from the boundary between isotropic and polar-cluster states previously reported in two-dimensional simulation studies and, unlike the latter, is not sensitive to the system size. We thus identify a generic feature of anisotropic active particles in three dimensions.