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DY: Fachverband Dynamik und Statistische Physik

DY 21: Granular Matter

DY 21.5: Vortrag

Mittwoch, 19. März 2025, 10:30–10:45, H43

Crystallization dynamics in a dense sphere system — •Frank Rietz and Matthias Schröter — Max Planck Institute for Dynamics and Self-Organization (MPIDS), Göttingen

When balls are thrown into a box and subsequently agitated, they tend to arrange themselves in a denser configuration, as observed in numerous experiments. However, a barrier is typically present at random close packing, which occupies approximately 64% of the available space. The spheres remain in their densest amorphous state and do not undergo a phase transition to a denser crystalline structure with a space-filling ratio of 74%. In our experiment, we successfully surmounted this barrier and observed the emergence of crystallization events from the disordered phase [1].

Initially, we observed the formation of groups of a few spheres that fluctuated between a disordered and a nucleated state. In rare instances when the balls remained in the ordered state, further investigation was conducted into their preceding conditions. This approach enables us to address the question of why the majority of precursors are not stable, while a few of them undergo growth to become part of the larger crystals of FCC and HCP structures that never dissolve.

[1] F. Rietz, C. Radin, H. L. Swinney, M. Schröter: Nucleation in sheared granular matter, Phys. Rev. Lett. 120, 055701 (2018)

Keywords: granular matter; crystallization; random close packing; sphere packing; jamming