A new family of stable quasicrystals.A new family of stable quasicrystals Under the right conditions, atoms in an aluminum-manganese alloy may line up into an arrangement that doesn't repeat itself at regular intervals yet appears to have the orderliness of a crystalline substance. Such a material, known as a quasiperiodic crystal, or quasicrystal, generally has an electron diffraction Electron diffraction The phenomenon associated with interference processes that occur when electrons are scattered by atoms to form diffraction patterns. pattern that shows a fivefold fivefold Adjective 1. having five times as many or as much 2. composed of five parts Adverb by five times as many or as much Adj. 1. symmetry. Ever since the discovery of the first quasicrystalline alloy, researchers have been looking for Looking for In the context of general equities, this describing a buy interest in which a dealer is asked to offer stock, often involving a capital commitment. Antithesis of in touch with. other materials with similar properties (SN: 3/7/87, p. 152). The latest addition to the quasicrystal family is an alloy made from gallium, magnesium and zinc. First prepared by Wataru Ohashi and Frans Spaepen of Harvard University Harvard University, mainly at Cambridge, Mass., including Harvard College, the oldest American college. Harvard College Harvard College, originally for men, was founded in 1636 with a grant from the General Court of the Massachusetts Bay Colony. , the samples are made up of icosahedral icosahedral a regular polyhedron with 20 triangular faces, 12 corners and 30 sides, having cubic symmetry with 5:3:2-fold axes. A common structural form for the capsid of many viruses including herpesviruses, adenoviruses, parvoviruses, reoviruses, picornaviruses and retroviruses. crystals as large as 100 microns across. Unlike all but one previously discovered quasicrystalline material, this alloy is stable. Heating doesn't transform it into a periodic crystal structure. "The discovery of a second stable quasiperiodic crystal will be of interest for diffraction studies of the structure and defects of these phases," the researchers report in the Dec. 10 NATURE. "Their low melting temperatures and the chemical behavior of the alloys make the crystals quite easy to prepare." |
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