An Etymological Dictionary of Astronomy and Astrophysics

A form of solid made up of ordered but non-repeating patterns of atoms, a symmetry that is forbidden for periodic crystals. In an ordinary crystal, only 1-, 2-, 3-, 4-, and 6-fold symmetries are possible, since these are the only symmetries that, when combined, can fill space. Prior to the discovery of quasicrystals, it was believed that 5-fold crystal symmetry could never occur. Quasicrystals are remarkable in that some of them display 5-fold or higher-fold forbidden symmetries. They are used as catalysts, in particular at high temperatures, to produce durable kinds of steel, like those used in objects such as razor blades and thin needles made specifically for eye surgery. The Nobel Prize in Chemistry 2011 was awarded to Daniel Schechtman for his discovery of quasicrystals in 1982.

See also: → quasi-; → crystal.