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<html><head><title>[cryst] 1 Introduction</title></head>
<body text="#000000" bgcolor="#ffffff">
[<a href = "chapters.htm">Up</a>] [<a href ="CHAP002.htm">Next</a>] [<a href = "theindex.htm">Index</a>]
<h1>1 Introduction</h1><p>
<p>
<a name = "I0"></a>
The <font face="Gill Sans,Helvetica,Arial">Cryst</font> package, previously known as <font face="Gill Sans,Helvetica,Arial">CrystGAP</font>, provides
functions for the computation with affine crystallographic groups,
in particular space groups. For the definition of the standard
crystallographic notions we refer to the International Tables
<a href="biblio.htm#Hah95"><cite>Hah95</cite></a>, in particular the chapter by Wondratschek <a href="biblio.htm#Won95"><cite>Won95</cite></a>,
and to the introductory chapter in <a href="biblio.htm#BBNWZ78"><cite>BBNWZ78</cite></a>. The principal
algorithms used in this package are described in <a href="biblio.htm#EGN97"><cite>EGN97</cite></a>.
<p>
The present version for <font face="Gill Sans,Helvetica,Arial">GAP</font> 4 has been considerably reworked from
an earlier version for <font face="Gill Sans,Helvetica,Arial">GAP</font> 3.4.4. Most of the porting to <font face="Gill Sans,Helvetica,Arial">GAP</font> 4
has been done by Franz Gähler. Besides affine crystallographic
groups acting from the right, also affine crystallographic groups acting
from the left are now fully supported. Many algorithms have been added,
extended, or improved in other ways.
<p>
Our warmest thanks go the Max Neunhöffer, whose extensive
testing of the <font face="Gill Sans,Helvetica,Arial">GAP</font> 4 version of <font face="Gill Sans,Helvetica,Arial">Cryst</font> in connection with <font face="Gill Sans,Helvetica,Arial">XGAP</font>
uncovered several bugs and led to many performance improvements.
<p>
<font face="Gill Sans,Helvetica,Arial">Cryst</font> is implemented in the <font face="Gill Sans,Helvetica,Arial">GAP</font> 4 language, and runs on any
system supporting <font face="Gill Sans,Helvetica,Arial">GAP</font> 4. However, certain commands may require
that other GAP packages such as <font face="Gill Sans,Helvetica,Arial">CaratInterface</font> or <font face="Gill Sans,Helvetica,Arial">XGAP</font> are installed.
In particular, the routines in Section <a href="CHAP002.htm#SECT008">Normalizers</a> are likely
to require <font face="Gill Sans,Helvetica,Arial">CaratInterface</font>, and the function WyckoffGraph (see <a href="CHAP002.htm#SSEC007.9">WyckoffGraph</a>)
requires <font face="Gill Sans,Helvetica,Arial">XGAP</font>. Both <font face="Gill Sans,Helvetica,Arial">CaratInterface</font> and <font face="Gill Sans,Helvetica,Arial">XGAP</font> may be available
only under Unix.
<p>
The <font face="Gill Sans,Helvetica,Arial">Cryst</font> package is loaded with the command
<pre>
gap> LoadPackage( "cryst" );
true
</pre>
<p>
<font face="Gill Sans,Helvetica,Arial">Cryst</font> has been developed by
<p>
<dl compact>
<dt>Bettina Eick <dd>
Fachbereich Mathematik und Informatik <br>
Technische Universität Braunschweig <br>
Pockelsstr. 14, D-38106 Braunschweig, Germany <br>
e-mail: <a href="mailto:b.eick@tu-bs.de">b.eick@tu-bs.de</a>
<p>
<dt>Franz Gähler <dd>
Fakultät für Mathematik,
Universität Bielefeld <br>
Postfach 10 01 31, D-33501 Bielefeld, Germany <br>
e-mail: <a href="mailto:gaehler@math.uni-bielefeld.de">gaehler@math.uni-bielefeld.de</a>
<p>
<dt>Werner Nickel <dd>
Fachbereich Mathematik, AG2,
Technische Universität Darmstadt, <br>
Schlossgartenstraße 7, D-64289 Darmstadt, Germany <br>
e-mail: <a href="mailto:nickel@mathematik.tu-darmstadt.de">nickel@mathematik.tu-darmstadt.de</a>
</dl>
<p>
For bug reports, suggestions and comments please please use
the issue tracker on GitHub:
<p>
<p>
<dl compact>
<dt><dd>
<a href="https://github.com/gap-packages/Cryst/issues/">https://github.com/gap-packages/Cryst/issues/</a>
</dl>
<p>
<p>
[<a href = "chapters.htm">Up</a>] [<a href ="CHAP002.htm">Next</a>] [<a href = "theindex.htm">Index</a>]
<P>
<address>cryst manual<br>September 2025
</address></body></html>
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