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The GAP 4 package Cryst, previously known as CrystGap, is the successor of the CrystGap package for GAP 3. During the porting process to GAP 4, large parts of the code have been rewritten, and the functionality has been extended considerably. Cryst provides a rich set of methods to compute with affine crystallographic groups, in particular space groups. In constrast to the GAP 3 version, affine crystallographic groups are now fully supported both in the representation acting from the right and in the representation acting from the left. The latter representation is the one preferred by crystallographers. There are also functions to determine representatives of all space group types of a given dimension.

Cryst is implemented in the GAP 4 language, and runs on any system supporting GAP 4. This version requires at least GAP version 4.5. It is recommended, however, to use the most recent version of GAP. Certain commands may need other GAP packages such as CARAT or XGAP. Both CARAT and XGAP are available only under Unix. CARAT may be required by functions that need to know normalizers or conjugators of finite unimodular groups in GL(n,Z) (see the section on normalizers of the Cryst manual). The function WyckoffGraph needs the package XGAP.

Cryst is distributed with GAP, and does not require any installation. It is loaded with the GAP command

gap> LoadPackage( "cryst" ); 

Cryst has been developed by

Bettina Eick,
Institut Computational Mathematics,
Fachbereich Mathematik und Informatik,
Technische Universität Braunschweig,
Pockelsstr. 14, D-38106 Braunschweig, Germany
e-mail: [email protected]

Franz Gähler,
Fakultät für Mathematik, Universität Bielefeld,
Postfach 10 01 31, D-33501 Bielefeld, Germany 
e-mail: [email protected]

Werner Nickel,
Fachbereich Mathematik, AG2,
Technische Universität Darmstadt,
Schlossgartenstrasse 7, D-64289 Darmstadt, Germany
e-mail: [email protected]

For bug reports, suggestions and other comments please use the issue tracker on the GitHub page of the package:

https://github.com/gap-packages/cryst/issues