Crystalline and polycrystalline regimes in a periodically sheared 2-dimensional system of disks

TL;DR

This study investigates how shear amplitude influences the structural regimes of monodisperse disks in a 2D system, revealing transitions from crystalline to polycrystalline states under different shear conditions.

Contribution

It identifies and characterizes the distinct crystalline and polycrystalline regimes in a sheared 2D disk system, highlighting the effects of shear amplitude on structural evolution.

Findings

Hexagonal crystallites form at low shear amplitudes.

Polycrystallites dominate at intermediate shear amplitudes.

Regimes are robust across certain pressures and frequencies.

Abstract

A layer of monodisperse circular steel disks in a nearly square horizontal cell forms, for shear amplitudes SA $\le$ 0.08, hexagonal close-packed crystallites that grow and merge until a single crystal fills the container. Increasing the shear amplitude leads to another reproducible regime, 0.21 $\le$ SA $\le$ 0.27, where a few large polycrystallites grow, shrink, and rotate with shear cycling, but do not evolve into a single crystal that fills the container. These results are robust within certain ranges of applied pressure and shear frequency.