CHEMISTRY 1000 Topics of Interest #5: Quasicrystals

Nobel Prize in Chemistry 2011 Prof. Dan Schechtman was awarded the 2011 Nobel Prize in Chemistry for his discovery of quasicrystals in 1982 while working at Technion – Israel Institute of Technology in Haifa, Israel. Like traditional crystals, quasicrystals are ordered, with the atoms arranged according to geometric patterns. Unlike traditional crystals, the atoms in a quasicrystal are not arranged in a lattice of repeating unit cells. 1 (last visited on Oct. 12, 2011)

Nobel Prize in Chemistry 2011 X-ray crystallography allows determination of crystal structure:

Nobel Prize in Chemistry 2011 The diffraction pattern for a traditional crystal could look like this: Note that there are six dots in the circle around the main spot. Four dots would also be consistent with a lattice of unit cells.

Nobel Prize in Chemistry 2011 The diffraction pattern for the first quasicrystals looked like this: Note that there are ten dots in the circle around the main spot. Cynics initially suggested that this was the result of analyzing a pair of fused crystals rather than a pure material.

Nobel Prize in Chemistry 2011 There is still an order to the arrangement of atoms in a quasicrystal but the atoms do not form a lattice of repeating unit cells. Instead, their geometric arrangement is similar to aperiodic mosaic tiling which has a certain mathematical order to it but no repeating unit:

Nobel Prize in Chemistry 2011

Since Schechtman’s original discovery, other synthetic quasicrystals have been produced and naturally occurring quasicrystals were discovered in mineral samples from a Russian river. Alloys containing quasicrystals have interesting physical properties (e.g. great strength that could be useful industrially) and continue to be studied.