title: Degenerate quasicrystal of hard triangular bipyramids.
abstract: We report a degenerate quasicrystal in Monte Carlo simulations of hard triangular bipyramids each composed of two regular tetrahedra sharing a single face. The dodecagonal quasicrystal is similar to that recently reported for hard tetrahedra [Haji-Akbari et al., Nature (London) 462, 773 (2009)] but degenerate in the pairing of tetrahedra, and self-assembles at packing fractions above 54%. This notion of degeneracy differs from the degeneracy of a quasiperiodic random tiling arising through phason flips. Free energy calculations show that a triclinic crystal is preferred at high packing fractions.
authors.affiliation: Department of Chemical Engineering, University of Michigan, Ann Arbor, 48109, USA.
authors.forename: Amir
authors.initials: A
authors.lastname: Haji-Akbari
authors.forename: Michael
authors.initials: M
authors.lastname: Engel
authors.forename: Sharon C
authors.initials: SC
authors.lastname: Glotzer