Frustrated Rotator Crystals and Glasses of Brownian Pentagons

Kun Zhao and Thomas G. Mason

Phys. Rev. Lett. 103, 208302 – Published 10 November 2009

Abstract

Two-dimensional Brownian dispersions of microscale pentagonal platelets exhibit rich structural and dynamical behavior as the particle area fraction, $ϕ_{A}$ , is increased. As $ϕ_{A}$ is raised above 0.66, a rotator crystal forms, and while in an equilateral hexagonal lattice, pentagons still explore all angles as they rotationally diffuse. At larger $ϕ_{A}$ , the interference of the tips of neighboring pentagons causes rotational dynamical heterogeneity; particle rotations become nonergodic, the hallmark of a frustrated rotator crystal. Upon further compression, the quenched-in rotational disorder and inability of pentagons to fully tile a flat plane creates spatial defects, precluding access to a dense striped crystalline packing.

Received 19 February 2009

DOI:https://doi.org/10.1103/PhysRevLett.103.208302

Authors & Affiliations

Kun Zhao^1,2 and Thomas G. Mason^1,2,3,*

¹Department of Physics and Astronomy, University of California–Los Angeles, Los Angeles, California 90095, USA
²Department of Chemistry and Biochemistry, and University of California–Los Angeles, Los Angeles, California 90095, USA
³California NanoSystems Institute, University of California–Los Angeles, Los Angeles, California 90095, USA

^*Corresponding author. mason@physics.ucla.edu

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Vol. 103, Iss. 20 — 13 November 2009

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