What is Laue symmetry?
The Laue group. describes the symmetry of the diffraction pattern. The Laue symmetry can. be lower than the metric symmetry of the unit cell, but never higher. That means: A monoclinic crystal with β = 90° is still monoclinic.
What are the 32 crystallographic point groups?
| Crystal System | 32 Crystallographic Point Groups | |
|---|---|---|
| Triclinic | 1 | |
| Monoclinic | 2 | |
| Orthorhombic | 222 | |
| Tetragonal | 4 | 4/mmm |
How is symmetry related to the space group?
Fourfold symmetry in the diffraction pattern corresponds to a fourfold axis in the space group (4, 4, 41, 42 or 43), threefold to a threefold, etc. If you take away the translational part of the space group symmetry and add an inversion center, you end up with the Laue group.
Which is an example of a symmorphic space group?
Symbols. All the other space groups are asymmorphic. Example for point group 4/mmm ( ): the symmorphic space groups are P4/mmm ( , 36s) and I4/mmm ( , 37s ); hemisymmorphic space groups should contain axial combination 422, these are P4/mcc ( , 35h ), P4/nbm ( , 36h ), P4/nnc ( , 37h ), and I4/mcm ( , 38h ).
Are there any space groups that are asymmorphic?
The 54 hemisymmorphic space groups contain only axial combination of symmetry elements from the corresponding point groups. Hemisymmorphic space groups contain the axial combination 422, which are P4/mcc ( , 38h ). The remaining 103 space groups are asymmorphic.
Which is the correct symbol for a space group?
The possible screw axes are: 2 1, 3 1, 3 2, 4 1, 4 2, 4 3, 6 1, 6 2, 6 3, 6 4, and 6 5 . In Schoenflies notation, the symbol of a space group is represented by the symbol of corresponding point group with additional superscript.