Difference between revisions of "Laue class"
From Online Dictionary of Crystallography
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| − | <Font color="blue"> Classes de Laue </Font> (''Fr'') | + | <Font color="blue">Classes de Laue</Font> (''Fr''); <Font color="red">Laue Klassen</Font> (''Ge''); <Font color="green">Clases de Laue </Font> (''Sp''); <Font color="black">Classi di Laue </Font>(''It''); <Font color="purple">ラウエ結晶類</Font>(''Ja''). |
Revision as of 14:28, 22 December 2016
Classes de Laue (Fr); Laue Klassen (Ge); Clases de Laue (Sp); Classi di Laue (It); ラウエ結晶類(Ja).
Definition
The Laue classes are eleven geometric crystal classes containing centrosymmetric crystallographic types of point groups and their subgroups. When absorption is negligible and Friedel's law applies, it is impossible to distinguish by diffraction between a centrosymmetric point group and one of its non-centrosymmetric subgroups; only point groups belonging to different Laue classes can then be distinguished.
| Laue classes | Non-centrosymmetric groups in the same Laue class |
| [math]{\bar 1}[/math] | 1 |
| 2/m | 2, m |
| mmm | 222, 2mm |
| [math]{\bar 3}[/math] | 3 |
| [math]{\bar 3}m[/math] | 32, 3m |
| 4/m | 4, [math]{\bar 4}[/math] |
| 4/mmm | 422, [math]{\bar 4}2m[/math], 42m |
| 6/m | 6, [math]{\bar 6}[/math] |
| 6/mmm | 622, [math]{\bar 6}2m[/math], 62m |
| [math]m{\bar 3}[/math] | 23 |
| [math]m{\bar 3}m[/math] | 432, [math]{\bar 4}[/math]32 |
See also
Chapter 3.1 of International Tables of Crystallography, Section A
Chapter 2.4 of International Tables of Crystallography, Section D