Structural type
A structural type encompasses all crystalline compounds that have their atoms at the same general locations. Structural types are usually named after prototypical examples (that is the most common mineral with that structure). Compounds with the same structural type are called iso-structural. The same structural type may encompass materials with very different combinations of elements.
Compatibility
Often one can replace elements with similar compatible ones to get from one compound to an other isostructural one in a quasi continuous fashion. See "isostructural bending" for examples.
While differences in atom sizes can be rather problematic for large scale epitaxal crystal growth in case of mechanosynthesis of very small crystolecules the strains usually won't add up to critical levels. On the contrary the atom size-difference may induce desired curvatures in the mechanosynthesized parts.
But note that structures with the same structural type are not always compatible.
Here's an example of a likely incompatible isostructural set: SiC, ZnO, AgI
The other way of a natural transition would be continuing with the same basic compound but changing the structural type. This can induce stresses but they can be negligible like e.g. transitioning from cubic to hexagonal diamond lattice.
Examples
- Zincblende structure (diamond lattice with two atom types)
- Wurtzite structure
- Rutile structure
- ...
(TODO: extend examples and elaborate on them)
Notes
Cristobalite SiO2 could be counted to the diamond lattice but there are oxygen atoms at the center of where only bonds should be. furthermore these oxygen links introduce kinks into the connections (at low temperatures - see here). So calling this compound isostructurality to the diamond lattice is maybe stretching it a bit.
The point here is that isostructurality is not an entirely sharp concept. It has blurry borders.
Related
- Pseudo phase diagram
- Gemstone like compound
- Isostructural bending
- Simple crystal structures of especial interest
External links
- Wikipedia: Isostructural
- Wikipedia: Isomorphism_(crystallography)
- Wikipedia (de): Structural type <<<
- Wikipedia (de): polytypism
- Structural type database (en): https://homepage.univie.ac.at/michael.leitner/lattice/index.html
- Structural type database (de): http://ruby.chemie.uni-freiburg.de/Vorlesung/Strukturtypen/alle.html
