Laue class

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], 4mm
6/m	6, [math]{\bar 6}[/math]
6/mmm	622, [math]{\bar 6}2m[/math], 6mm
[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