Difference between revisions of "Isostructural bending"

Revision as of 13:22, 12 July 2017

By substituting compatible elements in a crystal structure (a specific structure type to be more concrete) one introduces stresses due to the different diameters of the new atoms. In thin rods and plates that are a only a few atomic layers across these stresses can partially relax by bending (strains). This can be useful for making cylindrical geometries like axle housings and helical geometries like guiding screws.

Examples

Carbon atoms in diamond or lonsdaleite (== hexagonal diamond) can be replaced with silicon atoms at any ratio. (In case of a 1:1 ratio one has the gemstone compound called moissanite.)

When there's a pseudo phase diagram between two different compounds with the same structure-type then in most cases it should be possible to do some checkerboard patterning. As a concrete example one can replace titanium with silicon in the rutile structure type (C4). This is effectively moving around in the rutile <=> stishovite pseudo phase diagram. In case of the rutile structure there are a lot of compatible elements thus one can extend the diagram to a triangle, a tetrahedron, a hyper-tetrahedron and so on.

Care must be taken though. Going all the way from a specific structure type like e.g. SiO₂ to the same structure type of CO₂ one ends up with a compound that is likely an explosive in bulk since CO₂ very much likes to be a molecular gas with strong and low energy C=O double bonds.

Related

• Bending induced by surface passivation.