Lone researcher gets chemistry Nobel for discovering quasicrystalline solids

By John Timmer |


The 10-fold symmetry of the electron diffraction pattern contains two five-fold symmetries.

Yesterday, the Physics Nobel Prize went to a group of researchers who found that what we expected about something as basic as the structure of the Universe was wrong. Today, the Chemistry Prize has gone to a lone researcher who overturned something even more basic: his discovery of what's now termed a quasicrystal actually triggered the redefinition of what a crystaline solid is.

It's easy to find a representation of a typical crystal in any chemistry textbook, which will typically show an orderly arrangement of atoms, spreading out to infinity. These crystals, which are as easy to find in the nearest salt shaker, look the same no matter which direction you look at them. There are a limited number of ways to build something with that sort of symmetry, and chemists had pretty much figured they identified all of them. In fact, the International Union of Crystallography had defined a crystal as, "a substance in which the constituent atoms, molecules, or ions are packed in a regularly ordered, repeating three-dimensional pattern."

Enter Israel's Daniel Shechtman, who was working with a rapidly cooled aluminum alloy with about 10-15 percent manganese mixed in. Schechtman put his sample under an electron microcsope to generate a diffraction pattern, in which electrons are bounced off the atoms in an orderly crystal structure, creating a bunch of bright and dark regions that tell us about the positions of the atoms themselves. The diffraction pattern Schechtman saw, shown above, didn't make any sense—it showed a 10-fold symmetry, something that any chemist, including Schechtman, would know was impossible.


Shechtman's notebook
Iowa State University
In fact, his notebook, which is also still around, has three question marks next to the point where he noted the sample's 10-fold symmetry.

more

http://arstechnica.com/science/news/2011/10/symmetry-free-quasicrystals-given-the-nobel-prize-in-chemistry.ars

Way to go.