Pentagon deposits unpack under gentle tapping

Abstract

We present results from simulations of regular pentagons arranged in a rectangular die. The particles are subjected to vertical tapping. We study the behavior of the packing fraction, number of contacts and arch distributions as a function of the tapping amplitude. Pentagons show peculiar features as compared with disks. As a general rule, pentagons tend to form less arches than disks. Nevertheless, as the tapping amplitude is decreased, the typical size of the pentagon arches grows significantly. As a consequence, a pentagon packing reduces its packing fraction when tapped gently in contrast with the behavior found in rounded particle deposits.