Densest versus jammed packings of bent-core trimers

Abstract

We identify putatively maximally dense packings of tangent-sphere trimers with fixed bond angles (θ = θ0) using a novel method, and contrast them to the disordered jammed states they form under quasistatic and dynamic athermal compression. Incommensurability of θ0 with 3D closepacking does not by itself inhibit formation of dense 3D crystals; all θ0 allow formation of crystals with φmax(θ0) > 0.97φcp. Trimers are always able to arrange into periodic structures composed of close-packed bilayers or trilayers of triangular-lattice planes, separated by "gap layers" that accomodate the incommensurability. All systems have φJ significantly below the monomeric value, indicating that trimers' quenched bond-length and bond-angle constraints always act to promote jamming. φJ varies strongly with θ0; straight (θ0 = 0) trimers minimize φJ while closed (θ0 = 120 • ) trimers maximize it. Marginally jammed states of trimers with lower φJ (θ0) exhibit quantifiably greater disorder, and the lower φJ for small θ0 is apparently caused by trimers' decreasing effective configurational freedom as they approach linearity. arXiv:1907.00035v1 [cond-mat.soft]

Optimal shapes of disk assembly in saturated random packings

“…Remarkably, a consistent trend was also found in the jammed packing of this species in 3D. 78 As for ITD and COD, the relative radius g r 1 and maximal overlap magnitude g o 1 determine their shapes (or configurations), yielding saturated packing densities, respectively. Specifically, COD just degenerates into a dimer with a single parameter.…”