Powder diffraction
In the earliest days of neutron scattering, the method was used to determine the structure of ice (the hydrogen positions being previously unknown) and to show that the predicted Neel antiferromagnetic state existed in Nickel Oxide (Nobel Prize in Physics, 1970). These and other early experiments led to the award of the 1994 Nobel Prize in Physics to Cliff Shull. A distinctive contribution was the invention of the Rietveld Method, named after Hugo Rietveld who originally studied at University of Western Australia, for fitting crystallographic models to whole diffraction patterns. This was first applied to neutron powder diffraction and only decades later taken up routinely for x-ray powder diffraction. In recent years, the structures of the high-temperature superconductors (Nobel Prize in Physics, 1987) were first determined by neutron powder diffraction, as was the antiferromagnetism in the parent compound La2CuO4, and the method is a crucial tool whenever an important new material is discovered, be they superconductors, C60 buckyballs, Nd2Fe14B11 hard magnets (discovered by General Motors, in a search for lighter starter motors), colossal magnetoresistive oxides (Siemens and Bell Laboratories), quasicrystals (which violate normal crystallographic rules and exhibit 5-fold symmetry), and so on.