Orientational Ordering in Athermally Sheared, Aspherical, Frictionless Particles

TL;DR

This study investigates how aspherical, frictionless particles behave under shear, revealing persistent orientational order and rotation near the spherical limit, with implications for understanding jamming and particle alignment.

Contribution

It provides the first detailed numerical analysis of orientational ordering in sheared, athermal, aspherical particles approaching spherical shape.

Findings

Non-monotonic nematic order parameter with packing fraction.

Finite nematic order parameter persists at jamming as particles become spherical.

Particles continue to rotate above jamming, with contact points along narrowest width.

Abstract

We numerically simulate the uniform athermal shearing of bidisperse, frictionless, two dimensional spherocylinders and three dimensional prolate ellipsoids. We focus on the orientational ordering of particles as an asphericity parameter $\alpha\to 0$ and particles approach spherical. We find that the nematic order parameter $S_2$ is non-monotonic in the packing fraction $\phi$, and that as $\alpha\to 0$ $S_{2}$ stays finite at jamming and above. The approach to spherical particles thus appears to be singular. We also find that sheared particles continue to rotate above jamming, and that particle contacts preferentially lie along the narrowest width of the particles, even as $\alpha\to 0$.