Difference between revisions of "Pseudo symmetry"
From Online Dictionary of Crystallography
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| − | <font color="blue">Pseudo symétrie</font> (< | + | <font color="blue">Pseudo symétrie</font> (''Fr''). <font color="red">Pseudosymmetrie</font> (''Ge''). <font color="black">Pseudo simmetria</font> (''It''). <font color="purple">擬対称</font> (''Ja''). <font color="green">Seudosimetría</font> (''Sp''). |
Latest revision as of 10:12, 17 November 2017
Pseudo symétrie (Fr). Pseudosymmetrie (Ge). Pseudo simmetria (It). 擬対称 (Ja). Seudosimetría (Sp).
A crystal space can in general be divided in N components S1 to SN. When a coincidence operation φ(Si)→Sj brings the ith component Si to coincide with the jth component Sj, for any i and j, φ is a symmetry operation of the space group.
Sometimes, φ brings Si close to, but not exactly on, the position and orientation of Sj; in this case the operation mapping Si onto Sj is not crystallographic but the linear and/or rotational deviation from a space group operation is limited. For this reason, it is preferable to describe the crystallographic operation φ as a pseudo symmetry operation.
Pseudo symmetry operations for the lattice play an important role in twinning, namely in the case of twinning by pseudomerohedry and twinning by reticular pseudomerohedry.