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matt (M, 34)
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    Disordered, quasicrystalline and crystalline phases of densely packed tetrahedra
    (University of Michigan)



    A, Ideal local packing motifs built from tetrahedral dice stuck together with modelling putty. The pentagonal dipyramid (a), the nonamer (b) and the icosahedron (c) maximize local packing density. The icosahedron can be extended by adding a second shell (d), but then the large gaps between the outer tetrahedra lower the density. The tetrahelix (e) maximizes packing density in one dimension. B–D, A quasicrystal with packing fraction φ = 0.8324 obtained by first equilibrating an initially disordered fluid of 13,824 hard tetrahedra using Monte Carlo simulation and subsequent numerical compression. The images show an opaque view of the system (B) and opaque and translucent views of two rotated narrow slices C and D. The white overlay in D shows the distinctive 12-fold symmetry of the dodecagonal quasicrystal. Corrugated layers with normals along the z axis are apparent in C. The colouring of the tetrahedra is based on orientation.

    Full Article (pay access):
    http://www.nature.com/nature/journal/v462/n7274/fig_tab/nature08641_F1.html#figure-title



    "The results of this research and the formation of quasicrystals offer some interesting and exciting possibilities on how it can be used in real-world applications. “This will enable the production of metamaterials, which are manmade materials that don’t exist in nature, with interesting physical and optical properties,” Palffy-Muhoray said. 'Applications are far-ranging, including high-resolution imaging useful for microscopy in medicine and materials science. This new packing method could enable the production of new kinds of materials, useful for computer chips, building materials and fabrics.'"

     http://www.redorbit.com/news/technology/1797791/breaking_the_tetrahedra_packing_record/index.html 

    Mon, Dec 14, 2009  Permanent link

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