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Buzz Blog: Quasicrystal Physics

The Nobel Prize in Chemistry is awarded to Dan Shechtman for the discovery of quasicrystals.

While he was on sabbatical at the National Bureau of Standards in April 1982, Dan Shechtman made a startling discovery. He found that certain rapidly-cooled alloys of aluminum and manganese he was studying produced electron diffraction patterns just as crystals do, but the patterns showed that the alloy had an unusual rotational symmetry. In fact, the symmetry was inconsistent with the patterns that effectively defined a crystal. Shechtman had inadvertently stumbled across a quasicrystal.

In normal crystals, atoms lie on three-dimensional lattices of cells. Each cell has an identical pattern of cells surrounding it. In a quasicrystal, the local arrangements of atoms are fixed, but each cell has a different configuration of cells nearby. Although the structures are strikingly similar to the quasiperiodic tilings invented by mathematician Roger Penrose (which Martin Gardner popularized in a 1977 Mathematical Games column in Scientific American), there was little in the crystallographic field to presage the experimental breakthrough. Shechtman himself did not immediately recognize the quasiperiodic structure in his sample, and was at first mystified by the diffraction pattern. "I knew the diffraction pattern was not from twins [which result from a common crystal defect]," recalls Shechtman from his office at Technion University in Israel, "but I did not come up with an explanation for what it was."

Quasicrystals would eventually inspire a tidal wave of activity in crystallography, mathematics, physics, chemistry, and material science. Initially, however, Shechtman's discovery was viewed with skepticism. "For two years I did not have anybody who believed my results and was usually ridiculed," says Shechtman. "The scandal of polywater was still in the air, and I feared for my scientific and academic career."

See Physics Central Buzz Blog:

Metallic Phase with Long-Range Orientational Order and No Translational Symmetry D.Shechtman, I. Blech, D. Gratias, and J.W. Cahn, Phys. Rev. Lett. 53, 1951 (1984), 2155 citations