Quasicrystals: Chance Favors the Prepared Mind

Daniel Rabinovich

doi:10.1515/ci.2014.36.2.16

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Quasicrystals: Chance Favors the Prepared Mind

Daniel Rabinovich

Veröffentlicht/Copyright: 27. März 2014

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Aus der Zeitschrift Chemistry International Band 36 Heft 2

Louis Pasteur’s famous dictum is beautifully exemplified by the serendipitous discovery of quasiperiodic crystals by Dan Shechtman, a Professor of Materials Science at the Technion–Israel Institute of Technology. It is a remarkable story of ingenuity and perseverance that started in the spring of 1982, when Shechtman was studying rapidly solidified aluminum-manganese alloys while on sabbatical at the U.S. National Bureau of Standards in Gaithersburg, Maryland. On 8 April, he was investigating the microstructure of a sample of nominal composition Al₆Mn using transmission electron microscopy (TEM) and X‑ray crystallography. Quite unexpectedly, he observed a diffraction pattern that strongly suggested the presence of a crystalline material with hitherto unknown icosahedral symmetry, including crystallographically forbidden fivefold rotation axes. The existence of such unusual species, exhibiting long-range order but limited translational symmetry, was initially met with broad skepticism, most notably by the renowned chemist Linus Pauling, and this delayed the publication of results until the end of 1984. However, a flurry of experimental and theoretical work by Shechtman and others in the ensuing years confirmed the structural properties of quasicrystals, and many additional examples—often ternary alloys of aluminum with other metals—were reported. In 1993, the International Union of Crystallography, tacitly acknowledging the nature of quasicrystals, modified its traditional definition of crystal from “a substance in which the constituent atoms, molecules, or ions are packed in a regularly ordered, repeating three-dimensional pattern” to “any solid having an essentially discrete diffraction diagram.”

The stamp illustrated herein was released by Israel Post on 3 December 2013 and is the first one that explicitly celebrates the International Year of Crystallography (2014) while honoring Dan Shechtman, the sole recipient of the 2011 Nobel Prize in Chemistry. The stamp’s design features a fivefold symmetric electron diffraction pattern and a TEM image of two flowerlike quasicrystals akin to the ones he originally observed almost 30 years earlier. Although claims of potential applications for quasicrystals range from low-friction coatings to reinforced polymer composites, researchers in the field are trying to avoid the kind of hype and unrealistic expectations prompted by the discovery of other novel materials (fullerenes, high-temperature superconductors) in the 1980’s.

Incidentally, in a 2009 Science paper, Paul Steinhardt (the Professor of Physics at Princeton University who coined the term quasicrystals a few weeks after Shechtman’s first publication) described the first naturally occurring quasicrystals!

For a candid account of the discovery of quasicrystals, see: Hargittai, I. Isr. J. Chem. 2011, 51, 1144-1152.

Written by Daniel Rabinovich <drabinov@uncc.edu>.

Published Online: 2014-03-27

Published in Print: 2014-03

Artikel in diesem Heft

https://doi.org/10.1515/ci.2014.36.2.16