Difference between revisions of "Polytypism"
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An element or compound is '''polytypic''' if it occurs in several structural modifications, each of which can be regarded as built up by stacking layers of (nearly) identical structure and composition, and if the modifications differ only in their stacking sequence. Polytypism is a special case of polymorphism: the two-dimensional translations within the layers are essentially preserved. | An element or compound is '''polytypic''' if it occurs in several structural modifications, each of which can be regarded as built up by stacking layers of (nearly) identical structure and composition, and if the modifications differ only in their stacking sequence. Polytypism is a special case of polymorphism: the two-dimensional translations within the layers are essentially preserved. | ||
Revision as of 04:40, 28 October 2006
Polytypisme (Fr).
Definition
An element or compound is polytypic if it occurs in several structural modifications, each of which can be regarded as built up by stacking layers of (nearly) identical structure and composition, and if the modifications differ only in their stacking sequence. Polytypism is a special case of polymorphism: the two-dimensional translations within the layers are essentially preserved.
Acta Cryst. (1984). A40, 399-404; "Nomenclature of Polytype Structures" Report of the International Union of Crystallography Ad-Hoc Committee on the Nomenclature of Disordered, Modulated and Polytype Structures
See also
Chapter 9.2 of International Tables of Crystallography, Volume C