Densest versus jammed packings of bent-core trimers

AD Griffith and RS Hoy, PHYSICAL REVIEW E, 100, 022903 (2019).

DOI: 10.1103/PhysRevE.100.022903

We identify putatively maximally dense packings of tangent-sphere trimers with fixed bond angles (theta = theta(0)), and contrast them to the disordered jammed states they form under quasistatic and dynamic athermal compression. Incommensurability of theta(0) with three- dimensional (3D) close packing does not by itself inhibit formation of dense 3D crystals; all theta(0) allow formation of crystals with phi(max) (theta(0)) > 0.97 phi(cp).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 accommodate the incommensurability. All systems have phi(J) significantly below the monomeric value, indicating that trimers' quenched bond-length and bond- angle constraints always act to promote jamming phi(J) varies strongly with theta(0); straight (theta(0) = 0) trimers minimize phi(J) while closed (theta(0) = 120 degrees) trimers maximize it Marginally jammed states of trimers with lower phi(J) (theta(0)) exhibit quantifiably greater disorder, and the lower phi(J) for small theta(0) is apparently caused by trimers' decreasing effective configurational freedom as they approach linearity.

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