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October 05, 2011
2011 Chemistry Nobel Prize for the Discovery of Quasicrystals
This year's Nobel Prize in Chemistry goes to Dan Shechtman of Technion –Israel Institute of Technology in Haifa, for the discovery of quasicrystals, unique materials exhibiting regular patterns that never repeat themselves. “Quasicrystals are binary or ternary intermetallic compounds with non-crystallographic diffraction symmetry, mostly tenfold and icosahedral”, explains Professor Walter Steurer of the Swiss Federal Institute of Technology in Zürich, who is an expert in crystallography. Shechtman first discovered the new materials in 1982 when he was studying a mix of aluminum and manganese under an electron microscope.
The configuration of quasicrystals was initially thought to be impossible, but today scientists are able to produce the unique materials in many laboratories worldwide. The first naturally occurring quasicrystals were found about two years ago in Russia. “There are approximately one hundred quasicrystal compositions known”, Steurer says. “Stable quasicrystals can be grown by conventional methods in the same way and with the same perfection and dimensions as normal, periodic crystals. Quasiperiodic structures have also been found recently in self-organized colloidal systems with 12- and 18-fold symmetries”, he adds.
Professor Emil Zolotoyabko, who holds the Abraham Tulin Academic Chair at Technion and has worked closely with Shechtman, is delighted by the news: “Today is a great day for Israeli science, for Technion, and for my Department of Materials Engineering at Technion”, he says. The researcher believes that the Nobel Prize is a very well-deserved recognition for his fellow scientist. “Danny is a great scientist and a great colleague. I started my scientific carrier at Technion when he was a Department Head. He not only hired me but also helped a lot during my first steps here”. Zolotoyabko, who became a Faculty member at the renown Israeli institute in 1993, says that the quasicrystals discovered by his colleague exhibit interesting physical properties that are currently under intensive investigation and development by a large number of researchers worldwide.
One of them is Professor Hans-Rainer Trebin of the University of Stuttgart (Germany), who simulates the structure–property relationship of these materials. “The new structures give rise to new physical properties which deviate from those of ordinary metals”, he says. “The influence of structure on properties is an old problem, which gained impetus by the discovery. Through numerical simulations we investigate where the atoms sit and how they move”. Trebin explains that the tools developed for quasicrystals can also be used for complex metallic alloys. These are solids with large unit cells, which contain up to 20000 atoms and are locally very similar to quasicrystals. “Such large unit cells leave freedom for tailoring physical properties, for example for thermopower –the conversion of temperature differences into electric current”.
According to Walter Steurer, the quasiperiodic long-range order present in quasicrystals causes a particular structure that leads to low electronic and thermal conductivity as well as to a low surface energy. “Applications which use these properties may be of interest”, he says. The Swiss scientist adds that so-called quasiperiodic metacrystals may also find important practical uses in optics, communications or coatings. “Photonic crystals are of interest for optical devices, to be used in the communications industry or in optical computers. Phononic crystals can be used as thermal (nanometer scale) or acoustic (meter scale) barriers”. His German colleague, Hans-Rainer Trebin, believes that in addition to the many potential practical applications of quasicrystalline materials, for example in the field of catalysis, the mathematical background behind them is also very interesting because quasicrystals can be described as three-dimensional cuts through higher dimensional periodic crystals. A fascinating aspect of these special materials is that the golden ratio of mathematics and art, the mathematical constant tau, occurs over and over again.
Image: Nobel Medal (© ® The Nobel Foundation). Source: nobelprize.org
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