Superstructure

From Online Dictionary of Crystallography

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(Created page with "<font color="blue">Surstructure </font> (''Fr''). <font color="black">Superstruttura </font> (''It''). <font color="purple">超構造 </font> (''Ja''). A '''superstructure''' i...")
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*[[Substructure]]
*[[Substructure]]
*Martin J. Buerger: ''Journal of Chemical Physics'' '''15''' (1947) 1-16.
*Martin J. Buerger: ''Journal of Chemical Physics'' '''15''' (1947) 1-16.
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[[Category:Crystal chemistry]]
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[[Category:Fundamental crystallography]]

Latest revision as of 09:24, 17 February 2019

Surstructure (Fr). Superstruttura (It). 超構造 (Ja).


A superstructure is a crystal structure S’ obtained from another crystal structure (called a basic structure) S under the following conditions:

  • the space group G’ of S is a subgroup of the space group G of S;
  • the translation subgroup T(G’) of S’ is a subgroup of translation subgroup T(G) of S, i.e. the unit cell of S’ is a supercell of the unit cell of S and the lattice of S’ is sublattice of the lattice of S;
  • the point group of P’ of S’ may either coincide with the point group P of S or be a subgroup of it;
  • at least one of the Wyckoff positions of S is split into two or more independent Wyckoff positions of S’ and the corresponding crystallographic orbits are occupied by chemically different atoms.
A structure S composed by a single crystallographic orbit
A structure S' obtained from S by reducing its translational symmetry. Atomic positions represented by a different colour are not equivalent in S' and are occupied by chemically different atoms. S is called a basic structure, S' a superstructure of S. Vertical lines expanding beyond the horizontal boundaries of the unit cell indicate the translations along the b direction that are lost in the superstructure.

See also