Relationships between structure, memory and flow in sheared disordered materials

A fundamental challenge regarding disordered solids is predicting macroscopic yield—the point at which elastic behaviour changes to plastic behaviour—from the microscopic arrangements of constituent particles. Yield is accompanied by a sudden and large increase in energy dissipation due to the onset of plastic rearrangements. This suggests that one path to understanding bulk rheology is to map particle configurations to their mode of deformation. Here, we subject two-dimensional dense colloidal systems to oscillatory shear, measure the particle trajectories and bulk rheology, and quantify particle microstructure using excess entropy. Our results reveal a direct relation between excess entropy and energy dissipation that is insensitive to the nature of interactions amongst particles. We use this relation to build a physically informed model that connects rheology to microstructure. Our findings suggest a framework for tailoring the rheological response of disordered materials by tuning microstructural properties. Whether and when a material deforms elastically or plastically depends on its microstructure. Experiments on two-dimensional colloidal systems show that in disordered materials, packing density, stress and a microstructure-related entropy govern deformations.