Difference between revisions of "Laue class"
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== Definition == | == Definition == | ||
| − | The Laue classes correspond to the eleven centrosymmetric point groups. When absorption is negligible and [[Friedel's law]] applies, it impossible to distinguish by diffraction between a centrosymmetric point group and one of its non-centrosymmetric subgroups. | + | The Laue classes correspond to the eleven centrosymmetric point groups. 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. |
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{| border cellspacing="0" cellpadding="5" align=center> | {| border cellspacing="0" cellpadding="5" align=center> | ||
| − | |Laue | + | |Laue classes||Non-centrosymmetric groups<br> having the same Laue class |
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| <math>{\bar 1}</math>|| 1 | | <math>{\bar 1}</math>|| 1 | ||
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|<math>m{\bar 3}m</math>|| 432, <math>{\bar 4}</math>32 | |<math>m{\bar 3}m</math>|| 432, <math>{\bar 4}</math>32 | ||
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Revision as of 07:45, 26 March 2006
Classes de Laue (Fr). Laue Klassen (Ge). Clases de Laue (Sp).
Definition
The Laue classes correspond to the eleven centrosymmetric point groups. 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.
| Laue classes | Non-centrosymmetric groups having 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
Section 3.1 of International Tables of Crystallography, Section A