Grad student Chris Burke has just published his paper “The role of curvature anisotropy in the ordering of spheres on an ellipsoid” in the journal Soft Matter along with co-authors Badel Mbanga, Zengyi Wei, Patrick Spicer, and Tim Atherton. This paper focuses on geometric frustration: spheres tend to form orderly hexagonal packings, but they can’t do this on a curved surface, so there must be defects in the packing. Chris uses simulations to study how the varying curvature on the surface of an ellipsoid affects the placement of defects on such surfaces.
An example of a simulated packing, with highlighted defects.

An example of a simulated packing, with highlighted defects.

One of the conclusions of this paper is that many defects are attracted to the highly curved regions of the surfaces. However, long chains of defects known as “scars” are found at the more softly curved regions. The paper also investigates extremely orderly symmetric packings that occur on specifically shaped surfaces at specific particle numbers. Finally, an experimental realization of the system being simulated is presented for the first time, created by Patrick Spicer and his undergraduate student Zengyi Wei at the University of New South Wales.
 

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