The initial definition of a crystal was that it is an object with flat faces. When diffraction studies were developed it turned out that crystal consists of a highly ordered particles and it is possible to isolate a small unique part of their structure - a unit cell - and the definition has been changed to rely on this fact. Nowadays by a crystal we mean any solid having an essentially discrete diffraction diagram. It is because in recent years scientists found that there are some solids with discrete diffraction pattern, but there is no possibility to choose any unit cell. This is the case of quasicrystals discovered by Shechtman (Chemistry Nobel Prize 2011), polytypes and incommensurately modulated crystals - these all are called aperiodic crystals. However modulated crystals are not exactly aperiodic - their structures can be described as periodic, but in more than three (up to six) dimensions...
Authors
Additional information
- Category
- Publikacja monograficzna
- Type
- rozdział, artykuł w książce - dziele zbiorowym /podręczniku w języku o zasięgu międzynarodowym
- Language
- angielski
- Publication year
- 2012
