(268e) Packings and Self-Assembly of a Family of Hard Truncated Triangular Bipyramids

Haji-Akbari, A., Yale University
Chen, E. R., University of Michigan

For decades, hard-core interactions have been extensively used as models of colloidal systems with short-range repulsions. In recent years, theoretical and computational studies of hard particles have received further attention due to a flurry of activity in manufacturing colloidal particles of varying shapes. One remarkable feature of hard particles is their ability to assemble themselves into complicated structures. For instance, hard tetrahedra [1] and hard triangular bipyramids [2] have been observed to form a dodecagonal quasicrystal. A recent study of hard truncated tetrahedra has revealed the formation of several atomic crystal isostructures such as diamond, beta-tin and high pressure lithium [3]. All these studies underscore how geometric anisotropy of a particular building block can give rise to complicated structures with potentially interesting optical, electrical and/or mechanical properties. In this work, we consider a family of hard truncated triangular bipyramids and observe eight distinct families of packings in this system. We also establish that the formation of the quasicrystal is robust in the system and can be observed for truncations as high as 45 per cent.

1. A. Haji-Akbari, M. Engel, A. S. Keys, X. Y. Zheng, R. Petschek, P. Palffy-Muhoray, S. C. Glotzer, Disordered, quasicrystalline and crystalline phase of densely-packed tetrahedraNature 2009 462: 773-777.

2. A. Haji-Akbari, M. Engel, S. C. Glotzer, Degenerate Quasicrystal of Hard Triangular BipyramidsPhys. Rev. Lett. 2011 107: 215702.

3. P. F. Damasceno, M. Engel, S. C. Glotzer, Crystalline Assemblies and Densest Packings of a Family of Truncated Tetrahedra and the Role of Directional Entropic ForcesACS Nano 2012 6(1), 609-614.