Non-harmonic excitations in disordered soft solids with pressure gradients

A large body of previous work has focused on using structural information to predict the failure of amorphous solids. However, most systems studied so far have been devoid of pressure or other large-scale mechanical gradients, although such gradients are common in many systems of interest, including high density active matter, aggregation under microgravity, and sandpiles. More broadly, understanding how soft solids respond to deformation geometries ranging from simple shear to disordered internal activity is important to elucidate principles of biological function and material design. Our recent work highlights that a class of structural indicators based on the harmonic approximation of the potential energy landscape (i.e. linear response) are not good predictors of active dynamics in systems with strong pressure gradients. Therefore, in this work, we focus on the non-linear response of particle packings. Specifically, we extend a class of non-harmonic structural indicators to ensure that they are well-defined in packings with strong mechanical gradients, and investigate whether these non-harmonic structural indicators can predict plastic rearrangements in such systems.