Local order and structural rearrangement in two-dimensional jammed systems under oscillatory shear

Amorphous, jammed systems are abundant in nature and utilized often in man-made materials. The way in which their disordered structure evolves under the application of shear stress is an area of active investigation with consequences in contexts ranging from earth science to cancer research. Identifying local structural characteristics that influence macroscopic dynamics in these materials remains an ongoing challenge, and previous work has indicated generally that particles with ordered local environments are less likely to dynamically rearrange under shear. Here, we expand on this preliminary conclusion, and quantify it concretely in a two-dimensional colloidal jammed system subject to oscillatory shear. We analyze local crystallinity and identify crystal grains in these systems. We track structural correlations over time, and find that crystalline particles that are more interior within grains are less likely to rearrange. Moreover, propensity to rearrange occurs in a hierarchy according to the degree to which particles are “protected” within the grains. In addition, structural correlations qualitatively change at strain amplitudes above yield, where elasticity and viscosity become comparable, implying a transition in structural memory in the system.