Order and Disorder in the Assembly of Granular Matter

Abstract:

We will examine the development of ordered and disordered phases with granular solids under various growth conditions.  The motivation for our study is not only to understand how the phases form but also to develop strategies for assembly of composite materials from single elements. We will first consider the familiar example of spherical grains deposited randomly inside a container in a gravitational field, and discuss conditions under which a fully ordered face centered cubic crystal can be grown using a template. The growth of disorder observed in experiments will be compared with minimal models of defect growth and propagation from layer to layer. Then, we will examine the response of a disordered packing to applied shear, and discuss the nucleation of various ordered phases, their shapes and orientation.  The growth of order will be compared with those observed in thermal hard sphere models. We will further discuss the effect of cohesive interactions by examining capillary aggregation, and spontaneous assembly of designed structures.