Study of the transition from amorphous to crystalline phase in a granular system under shearing and vibration

We study a slightly tilted bidimensional vibrated hard-sphere system under periodic shearing as a macroscopic model for glass-crystal phase transition. The system starts close to a random closed packed (RCP) state, modeling an amorphous solid, and rearranges into a hexagonal closed packed (HCP) crystal configuration. The vibration is fixed in amplitude and frequency, modeling a constant temperature. Periodical deformations of a rhomboidal shape boundary provide an alternating shearing. Under these conditions, the system evolves toward an ordered arrangement by an annealing process. To characterize the order, we used the sixth-bond-orientational order parameter ψ6′ which is determined for each particle using the nearest neighbors obtained from the Delaunay criterion triangulation with the additional imposition that neighbors be in touch with the particle. We report the results of seven experimental cases where the maximum deformation shear amplitude is varied. We found correlations between shear amplitude with the average of the sixth-bond-orientational order parameter. The results indicate that the cyclic perturbation determines complex oscillatory hexagonal order dynamics. It is found correlations between the sheared boundary’s acceleration with the rate of change of ψ6′.