Materials Science and Engineering
Dan Shechtman was born on January 24, 1941 in Tel Aviv, Israel. He earned his Bacheler’s of Science, Master’s of Science, and Ph.D. degrees at the Technion in Israel, in the field of Materials Engineering. He did postdoctoral work, supported by a fellowship from the National Research Council, at the Wright Patterson Air Force Base (USA) from 1972 to 1975. In 1975 he accepted a position as Lecturer at the Technion, and rose through the academic ranks there to become Distinguished Professor and to hold the Philip Tobias Chair. During his years at the Technion, he also held positions as visiting scientist at several US institutions, including the National Institute of Standards and Technology (NIST). In 2004, he accepted a partial appointment at Iowa State University as a Professor of Materials Science and Engineering, and a position as Associate of the Ames Laboratory. In 2011 he was awarded the Nobel Prize in Chemistry for his discovery of quasicrystals. He made this discovery while working at NIST on April 8, 1982 and he championed it in the years that followed. This ignited a scientific revolution that changed the way we understand solid matter. His courage and clarity of vision during that turbulent, exciting period are an inspiration to scientists everywhere. He has won numerous other prizes for this achievement, including the International Award for New Materials of the American Physical Society (1987), the Wolf Prize in Physics (1999), and the European Materials Research Society’s 25th Anniversary Award (2008)—to name just a few.
A brief description of his discovery, and some of its ramifications, follows. An excellent source of information can also be found in the following article: “‘There is no such animal’—Lessons of a Discovery,” by Istvan Hargittai, published in Structural Chemistry (2011) 22:745-748, DOI 10.1007/11224-011-9792-1.
Dan Shechtman’s studies and training led him to be an excellent metallurgist and a superb electron microscopist. In April of 1982, he took a few months from his permanent appointment on the faculty of the Technion, to carry out research at the U.S. institution then called the National Bureau of Standards (now known as NIST). The goal of the research was to search for new rapidly-quenched Al-based alloys. Because rapid quenching yields very small-sized grains, only a microscopic probe could be used in this search. Transmission electron microscopy (TEM), in particular, was well-suited for the project, since it provides a means to measure real-space structure and diffraction in very small, thin samples. At one certain composition of Al and Mn (Al6Mn), Dan found a diffraction pattern that was tenfold symmetric. His further experiments revealed twofold and threefold axes at specific angles relative to the tenfold—angles that could only be reconciled with icosahedral symmetry. This was revolutionary.
An icosahedron contains fivefold, twofold, and threefold rotational axes. (A fivefold axis “masquerades” as tenfold in a typical diffraction experiment, and this is why Dan originally observed a tenfold pattern rather than fivefold.) A fivefold axis is, however, forbidden in a periodic crystal. At the time of Dan’s discovery, a deeply ingrained belief in the materials science community was that all crystals—all ordered solids—were periodic. Hence, order was incompatible with fivefold symmetry. This is the reason why Dan’s discovery ignited a storm of controversy and criticism.
At the time, it was known that crystalline materials could twin in such a way as to generate false indications of forbidden symmetries, including fivefold symmetry. Indeed, quasicrystals had been “discovered” prior to Dan Shechtman’s work, but they were not recognized for what they were. They were either labeled as twins, or simply as unidentified phases. The field was limited by the techniques available to it. The technique that enabled Dan’s discovery, the one that had been absent in the earlier investigations, was TEM. With this, Dan—being a very gifted electron microscopist—could determine whether twinning was a possible explanation. He generated a series of dark-field images, and also performed a convergent-beam experiment. These showed that the icosahedral symmetry was not due to twinning, but rather was present on the atomic scale. He was the right scientist, in the right place at the right time.
Dan’s discovery was published in Physical Review Letters in 1984. He had three co-authors: John Cahn, Denis Gratias, and Ilan Blech. Blech was the first to believe Dan’s data, and to help construct a model that could explain it. Cahn, the renowned materials scientist, helped Dan to write the paper in a way that would garner the attention it deserved. And Gratias, a crystallographer, provided a mathematical underpinning. It is widely acknowledged, however, that Shechtman is the scientist who deserves credit for the discovery, and for bringing it to the attention of the scientific community.
It was certainly Shechtman who withstood the public criticism. This came most intensely from Linus Pauling, famous for such public statements as ‘Rest easy, my friends. There is no such thing as quasicrystals. There are only quasi-scientists.’ But Shechtman had the remarkable tenacity to hold his ground. If he had not done so, the topic could have easily become muddled, and its resolution unclear. However, the scientific community was attracted (as always) by controversy. The community generated experimental data which eventually swung the opinion in Shechtman’s favor. Today, the very textbooks that were pointed out to Dan as proof that his claim was impossible, have been modified to include discussions of quasicrystals and aperiodic order. This controversy subsequent paradigm-shift bears all the hallmarks of a classical scientific revolution.
An active, interdisciplinary community grew up out of Shechtman’s discovery. His discovery stimulated new mathematics (particularly tilings and random tilings), new physics (e.g. transport, magnetism, and electronic structure), new materials science (e.g. new methods in electron microscopy, discovery of new phases, new understanding of friction on hard metallic surfaces, and inroads into the art of sample growth), and new chemistry (e.g. new heterogeneous catalysts). The discovery of thermodynamically stable phases in the late 1980’s advanced the field tremendously, because it allowed large, thermally-stable samples to be prepared whose properties could be characterized. From this came the realization that quasicrystals have unusual combinations of physical properties. For instance, most of the known quasicrystals are hard, brittle, and poor thermal conductors. They also exhibit low surface energy and low friction coefficients. The quest for applications based upon these physical properties has been described in detail in a book by Dubois (cited below).
D. Shechtman, I. Blech, D. Gratias, and J.W. Cahn, “Metallic Phase with Long-Range Orientational Order and No Translational Symmetry.” Physical Review Letters 53, 1951 (1984).
I. Hargittai, “Quasicrystal Discovery: A Personal Account.” The Chemical Intelligencer, 25 (1997).
J.M. Dubois, Useful Quasicrystals. World Scientific, Singapore, (2005).
R. Lifshitz, D. Shechtman and S. I. Ben-Abraham, Ed. Quasicrystals: The Silver Jubilee, Proceedings of a Conference held in Tel Aviv, Israel, in 2007. Philosophical Magazine 88 (2008) 1879-2351.
T.S. Kuhn, The Structure of Scientific Revolutions. The University of Chicago Press, (1996).
A.-P. Tsai, “Back to the Future—An Account of the Discovery of Stable Quasicrystals.” Accounts of Chemical Research 36, 31 (2003).
- Ph.D. Materials Engineering, Technion, Israel Institute of Technology, 1972
- M. Sc. Materials Engineering, Technion, Israel Institute of Technology, 1968
- B. Sc. Mechanical Engineering, Technion, Israel Institute of Technology, 1966
- Advanced characterization methods
- Microstructural design and processing