# Difference between revisions of "Geometric crystal class"

### From Online Dictionary of Crystallography

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== Definition == | == Definition == | ||

− | '''Geometric crystal classes''' (or simply 'crystal classes') classify the symmetry groups of the external shape of macroscopic crystals, namely according to the morphological symmetry. There are 10 two-dimensional geometric crystal classes and 32 three-dimensional geometric crystal classes, in one to one correspondence with the 10 and 32 point groups in ''E''<sup>2</sup> and ''E''<sup>3</sup>, respectively. | + | '''Geometric crystal classes''' (or simply 'crystal classes') classify the symmetry groups of the external shape of macroscopic crystals, namely according to the morphological symmetry. There are 10 two-dimensional geometric crystal classes and 32 three-dimensional geometric crystal classes, in one to one correspondence with the 10 and 32 types of point groups in ''E''<sup>2</sup> and ''E''<sup>3</sup>, respectively. |

== See also == | == See also == |

## Revision as of 12:48, 17 March 2009

Classe cristalline géométrique (*Fr*); Geometrische Kristallklasse (*Ge*); Clase cristallina geométrica (*Sp*); Classe cristallina geometrica (*It*). 幾何晶族 (*Ja*)

## Definition

**Geometric crystal classes** (or simply 'crystal classes') classify the symmetry groups of the external shape of macroscopic crystals, namely according to the morphological symmetry. There are 10 two-dimensional geometric crystal classes and 32 three-dimensional geometric crystal classes, in one to one correspondence with the 10 and 32 types of point groups in *E*^{2} and *E*^{3}, respectively.

## See also

- Arithmetic crystal class
- Section 8.2.4 of
*International Tables for Crystallography, Volume A*