Laue class

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 impossible to distinguish by diffraction between a centrosymmetric point group and one of its non-centrosymmetric subgroups.

Laue class	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

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Laue class	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