
The GAP 4 package CrystCat provides a catalog of crystallographic 
groups of dimensions 2, 3, and 4 which covers most of the data contained 
in the book "Crystallographic groups of four-dimensional space" by 
H. Brown, R. B\"ulow, J. Neub\"user, H. Wondratschek, and H. Zassenhaus 
(John Wiley, New York, 1978). This catalog was previously available in 
the library of GAP 3. The present version for GAP 4 has been moved into 
a separate package, because it requires the package Cryst, which is
loaded automatically. The benefit of this is that space groups 
extracted from the catalog now have the rich set of methods provided 
by Cryst at their disposal, and are no longer dumb lists of generators. 
Moreover, space groups are now fully supported in both the representation
acting from the left and the representation acting from the right.

To install CrystCat, just unpack crystcat.zoo in the pkg subdirectory
of your GAP installation (or in the pkg subdirectory of any other
GAP root directory) with the following command:

unzoo -x crystcat.zoo

CrystCat is then loaded with the GAP command

gap> RequirePackage( "crystcat" ); 

The catalog was brought into GAP format, and ported later to GAP 4 by 

    Volkmar Felsch, Lehrstuhl D fuer Mathematik, RWTH Aachen,
    volkmar.felsch@math.rwth-aachen.de

The integration with Cryst is by

    Franz G\"ahler, Institut f\"ur Theoretische und Angewandte Physik,
    Universit\"at Stuttgart, gaehler@itap.physik.uni-stuttgart.de

Please sent bug reports to any of these email addresses.
