“The mostimportantthing about thequasicrystals istheir meaningfor fundamentalscience. They haverewritten thefirst chapter inthe textbooks ofordered matter.”
Prof. Sven Lidin, Professor of InorganicChemistry, Lund University. Member of the Nobel Committee for Chemistry
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| In the mid-1970s, mathematician Prof. Roger Penrose, of Oxford University, created an aperiodic mosaic, with a pattern that never repeats itself, with just two different rhomboid tiles (a fat rhombus and a thin rhombus). |
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The page in Dan Shechtman’s lab logbook recording his April 8th, 1982, discovery.
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| Meeting at the National Institute of Standards and Technology (NIST) in 1985 just months after shaking the foundations of materials science with publication of his discovery of quasicrystals, Dan Shechtman, winner of the 2011 Nobel Prize in Chemistry, discusses the material’s surprising atomic structure with collaborators. From left to right are Shechtman; Frank Biancaniello, NIST; Denis Gratias, National Science Research Center, France; John Cahn, NIST; Leonid Bendersky, Johns Hopkins University (now at NIST); and Robert Schaefer, NIST. |
200 years and nobody noticed?
How could quasicrystalshave evaded the communityof crystallographers for solong? In addition to the vitalinput of his collaborators,says Shechtman, thediscovery required severalcritical components. First,it was necessary to makeesoteric, rather than useful,rapidly cooled alloys.Then a researcher wouldhave to study them witha transmission electronmicroscope, performnumerous detailed analyses,and finally face a fortress ofresistance to changing therules of understanding thematerial world.
A quasiperiodic crystal is a structure that is ordered but not periodic. In quasicrystals, the symmetry is broken: there are regular patterns in the structure but the structure never repeats itself. A shifted copy will never match exactly.
Back in the ’80s when the new class of matter was accepted only by a few, it was dubbed
“Shechtmanite,” after the man who led the field through conception and infancy. The name “Shechtmanite” carried the risk of humiliation if the material turned out to be “twinning” (the intergrowth of two separate crystals on a shared lattice), as claimed by Shechtman’s opponents.
“Shechtmanite,” after the man who led the field through conception and infancy. The name “Shechtmanite” carried the risk of humiliation if the material turned out to be “twinning” (the intergrowth of two separate crystals on a shared lattice), as claimed by Shechtman’s opponents.
Quasicrystal structure can be understood through the mathematical theory of tiling.
Initially, however, Shechtman’s discovery was viewed with skepticism. “The scandal of
polywater was still in the air, and I feared for my scientific and academic career,” says Shechtman.
Initially, however, Shechtman’s discovery was viewed with skepticism. “The scandal of
polywater was still in the air, and I feared for my scientific and academic career,” says Shechtman.
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| (l-r) John Werner Cahn, Dan Shechtman, Ilan Blech and Denis Gratias together on the occasion of an international congress on quasicrystals in France, 1995. © CNRS Photothèque – Pierre Grumberg |
Shechtman returned to Technion, where Dr. Ilan Blech was the only colleague who not only believed in him but who agreed to cooperate with him. Blech was able to decipher Shechtman’s experimental findings and offered an explanation, known as the Icosahedral Glass Model.
Together, the researchers wrote an article that contained the model and the experimental results, and submitted it to the Journal of AppliedPhysics in the summer of 1984. The paper was rejected, resubmitted to the journal Metallurgical Transactions, and was published in 1985.
In November 1984, Physical ReviewLetters published Shechtman’s discovery in a scientific paper coauthored with three other scientists: Ilan Blech (Israel), Denis Gratias (France) and John Cahn (USA). Wider acclaim followed, mainly from physicists and mathematicians and later from crystallographers.
Pioneering contributors to the field of quasicrystals are Prof. Dov Levine of the Technion Faculty of Physics and Prof. Paul Steinhardt of Princeton University. They made the
connection between a theoretical tenfold symmetry model proposed by Prof. Alan Mackay and Shechtman’s diffraction pattern, and developed the mathematical model for the structure of non-periodic icosahedral phases found in metallic alloys. Steinhardt and Levine published an article in 1984 where they described quasicrystals and their aperiodic mosaics.
connection between a theoretical tenfold symmetry model proposed by Prof. Alan Mackay and Shechtman’s diffraction pattern, and developed the mathematical model for the structure of non-periodic icosahedral phases found in metallic alloys. Steinhardt and Levine published an article in 1984 where they described quasicrystals and their aperiodic mosaics.
Quasicrystals first got their name in this article!
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Dov Levine (left) with Paul Steinhardt (right)
at the Technion Faculty of Physics in 2006.
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In August 1986, David R. Nelson wrote in Scientific American, “Shechtmanite quasicrystals are no mere curiosity. The study of quasicrystals has tied together two existing branches of theory: the theory of metallic glasses and the mathematical theory of aperiodic tilings. In doing so it has brought new and powerful tools to bear on the study of metallic alloys. Questions about long- and short-range icosahedral order should occupy solid-state physicists and materials scientists for some time to come.”
Today, over 40 scientific books have been dedicated to quasiperiodic crystals, and the International Union of Crystallography has changed its basic definition of a crystal, reducing it to the ability to produce a clear-cut diffraction pattern and acknowledging that crystallographic order can be either periodic or aperiodic.