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Center for Nonlinear Studies |
Mechanically stable packings of frictionless disks with contact interactions form through fast quenches at random close packing (RCP). However, for frictional particles with static friction coefficient μ greater than μ*, the packing density slides toward random loose packing (RLP) at large friction. I will discuss how the crossover from random close to random loose packing can be explained by identifying a novel geometric phase transition through simulations of frictional bidisperse disks. The rotational content of low energy vibrational modes at jamming onset drastically changes from co-rotating contacting particles for low friction to counter-rotating, gear-like, for μ greater than μ* and the groups of particles with gear-like dynamical contributions percolate at μ*. The emergence of this "gear rigidity" transition provides deep insights for possible universal mechanisms to optimize the density of random packings.
Host: Cynthia Reichhardt,