The program PSEUDO looks for a pseudosymmetry in a structure among the (minimal) supergroups of the structure's space group.
The first step in the program is the input of the structure's data. The data can be given using the form or it can be loaded from a CIF file. The necessary data for the structure consists in the number of its space group in the International Tables for Crystallography, Vol A, the lattice parameters (in A and degrees), the number of the atoms in the asymmetric unit and the corresponding atomic positions.
Then, it's necessary to select among what type of supergroups the search is performed. The available options are:
- Minimal supergroups
- Supergroups for a defined cell multiplication
- Supergroup for a well-known transformation matrix
Another option (only for triclinic and monoclinic groups) is to check first the pseudosymmetry of the given cell (obtaining the possible lattice transformations for a given angular tolerance and checking if they are compatible with a space supergroup transformation)
Finally, the program needs a maximum allowed tolerance for pseudosymmetry calculations, i.e., the maximal allowed displacement of the atoms from their high symmetry position in Angstroms. Normally a default value between 0.75-1A is a good choice.
When you have filled all of the data, click on the [Show] button to search for pseudosymmetry with respect to the chosen supergroups option.
To get a tutorial about this program click here.
If you are using this program in the preparation of a paper, please cite it in the following form:
E. Kroumova, M. I. Aroyo, J. M. Perez-Mato, S. Ivantchev, J. M. Igartua and H. Wondratschek. "PSEUDO: a program for a pseudosymmetry search". J. Appl. Cryst. (2001), 34, 783-784.
If you are interested in other publications related to Bilbao Crystallographic Server, click
here.
|
|
Please, enter structure data in the text area (or load CIF file).
Select supergroups type for pseudosymmetry search.
|
|
|
[*] In triclinics and monoclinics space groups, the calculation of supergroups is not complete due limitations of SUPERGROUPS program. Anyway, if you know the transformation matrix you can use the option 3 in these cases.
|
Enter the tolerance (maximum allowed distance) for pseudosymmetry search.
|
Pseudosymmetry search