  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.
