Pentagon deposits unpack under gentle tapping

Abstract

We present results from simulations of regular pentagons arranged in a rectangular box. The particles are subjected to vertical tapping. We study the packing fraction, number of contacts, and arch size distribution as a function of the tapping amplitude. Compared with disks, pentagons show peculiar features. As a general rule, pentagons tend to form fewer arches than do 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.