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Shape-induced frustration of hexagonal order in polyhedral colloids
Roel P A Dullens1, Maurice C D Mourad, Dirk G A L Aarts
1Van't Hoff Laboratory for Physical and Colloid Chemistry, Debye Institute, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands.
Physical Review Letters
|February 21, 2006
Summary
Nonspherical particle shapes disrupt hexagonal packing in dense colloidal systems. Despite suppressed translational order, bond-orientational order persists, revealing a hexatic-like structure in polyhedral colloids.
Area of Science:
- Colloid science
- Materials science
- Statistical physics
Background:
- Dense colloidal systems are model systems for studying phase transitions and ordering phenomena.
- Particle shape and size polydispersity significantly influence the macroscopic properties and microscopic structures of colloidal assemblies.
Purpose of the Study:
- To investigate the impact of nonspherical particle shape and shape polydispersity on the structure of densely packed hard colloidal particles.
- To analyze the ordering behavior at the wall of concentrated colloidal suspensions with monodisperse but shape-polydisperse polyhedral particles.
Main Methods:
- Real-space observation using confocal microscopy.
- Analysis of particle arrangements and structural correlations in the first layer at the wall.
Main Results:
- Significant deviations from a hexagonal lattice were observed in the first layer of shape-polydisperse polyhedral colloids.
- Deviations were characterized as bond-orientational fluctuations forming percolating "mismatch lines."
- Shape-induced geometrical frustration suppressed translational order but retained bond-orientational order.
Conclusions:
- The structure of densely packed nonspherical colloids deviates from ideal hexagonal packing due to shape polydispersity.
- A hexatic-like structure, characterized by retained bond-orientational order despite suppressed translational order, is identified in polyhedral colloids.