Crystallization in Cyclically Sheared Granular Matter

An understanding of how crystal formation is initiated within a homogeneous disordered state can provide insights into the old problems of glass formation and crystallization in fluids.  Experiments over the past half century have shown that granular materials, under repeated small amplitude disturbances, will reach a maximum volume fraction called random close packed (RCP), which has been found to be 0.63-0.66. This talk will describe an experiment and numerical simulations on spheres where the position of every sphere’s center at each time step is determined to high precision. For repeated small amplitude shear, the spheres spontaneously form crystallites that begin to grow rapidly if they reach a critical size of 10-15 spheres. This onset of crystallization occurs at volume fraction 0.646±0.001. Neither friction nor gravity is essential for this homogeneous crystallization.

Reference:

Homogeneous Crystallization in Cyclically Sheared Frictionless Grains

Weiwei Jin, Corey S. O’Hern, Charles Radin, Mark D. Shattuck,

and Harry L. Swinney

Physical Review Letters 125, 258003 (2020)

DOI: 10.1103/PhysRevLett.125.258003

Part of the NSCS webinar series https://softmatterisrael.wixsite.com/nscs