Dresden 2014 – wissenschaftliches Programm
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 37: Poster Session 2
CPP 37.70: Poster
Mittwoch, 2. April 2014, 15:00–19:00, P3
First order phase transition at Random Close Packing of spheres — •Frank Rietz1, Charles Radin2, Harry L. Swinney3, and Matthias Schröter1 — 1Max Planck Institute for Dynamics and Self-Organization (MPIDS), 37077 Goettingen, Germany — 2University of Texas at Austin, Department of Mathematics — 3University of Texas at Austin, Center for Nonlinear Dynamics
The name Random Close Packing refers to the experimental observation that some ways of packing of monodisperse beads (like vertical vibration or sedimentation) cannot exceed a volume fraction of about 64%. There are several competing theories for this phenomenon. However, it is possible to surpass the random close packing limit by cyclic shearing [1]. We investigate the three-dimensional distribution of particles in such a shear cell. Below the Random Close Packing density the packing compacts by reconfiguring particles in denser but disordered arrangements. At Random Close Packing the compaction process saturates involving all particles in tetrahedral-like configurations. These structures are locally dense however compose not the maximum global density that is achievable for spheres. Further increase of the density is only possible by large-scale bead rearrangements that lead to crystalline nuclei and ordered particle ensembles. From the distribution of local volumes around every sphere a first order phase transition is observed. The transition is visible in the polytetrahedra network, angular order parameter, local clusters, and Voronoi shapes.
[1] Nicolas; Eur. Phys. J. E 3, 309 (2000).