Actions

Difference between revisions of "Symmetry operation"

From Online Dictionary of Crystallography

m (lang)
(link)
Line 6: Line 6:
 
The two configurations/objects can be either congruent or enantiomorphous. Correspondingly, the symmetry operations are classed into two kinds:
 
The two configurations/objects can be either congruent or enantiomorphous. Correspondingly, the symmetry operations are classed into two kinds:
 
* '''symmetry operations of first kind''': they relate congruent objects and consist of translations, rotations and screw rotations;
 
* '''symmetry operations of first kind''': they relate congruent objects and consist of translations, rotations and screw rotations;
* '''symmetry operations of second kind''': they relate enantiomorphous objects and consist of inversion, reflections, rotoinversions, and glide reflections. There exist a 1:1 correspondence between rotoinversion and rotoreflections: the latter are more used in Schoenflies notation, whereas rotoinversions are preferred in Hermann-Mauguin notation.
+
* '''symmetry operations of second kind''': they relate enantiomorphous objects and consist of inversion, reflections, rotoinversions, and glide reflections. There exist a 1:1 correspondence between rotoinversion and rotoreflections: the latter are more used in Schoenflies notation, whereas rotoinversions are preferred in [[Hermann-Mauguin symbols|Hermann-Mauguin]] notation.
  
 
A symmetry operation can be performed about a [[symmetry element]]. Exceptions are the identity and the pure translations, for which a symmetry element is not defined.
 
A symmetry operation can be performed about a [[symmetry element]]. Exceptions are the identity and the pure translations, for which a symmetry element is not defined.
  
 
[[Category:Fundamental crystallography]]
 
[[Category:Fundamental crystallography]]

Revision as of 13:46, 24 November 2016

Opération de symétrie (Fr); Symmetrie-Operationen (Ge); Operación de simetría (Sp); Ooerazione di simmetria (It); 対称操作 (Ja).


A symmetry operation is an isometry, i.e. a transformation under which two objects, or two configurations or an object, are brought to coincide. A symmetry operation is a Euclidean mapping: to each point of the first configuration there corresponds a point of the second configuration, the distances between two points are kept by the transformation, as are the angles.

The two configurations/objects can be either congruent or enantiomorphous. Correspondingly, the symmetry operations are classed into two kinds:

  • symmetry operations of first kind: they relate congruent objects and consist of translations, rotations and screw rotations;
  • symmetry operations of second kind: they relate enantiomorphous objects and consist of inversion, reflections, rotoinversions, and glide reflections. There exist a 1:1 correspondence between rotoinversion and rotoreflections: the latter are more used in Schoenflies notation, whereas rotoinversions are preferred in Hermann-Mauguin notation.

A symmetry operation can be performed about a symmetry element. Exceptions are the identity and the pure translations, for which a symmetry element is not defined.