is a program system for analysing crystal structures using graphtheoretic and algebraic methods.

Part of the system is available on the net. At present we offer algorithms for computing

- the Liebau classification of silicates (for some peculiarities see
**implementation of Liebau classification**) - rings in tetrahedral networks (including edge and node coverings by rings)
- coordination polyhedra (offering 6 different methods) and topologically equivalent clusters of polyhedra

(Polysearch)

can be analysed with the possibility to freely choose elements as central atoms or ligands.

Analysis is performed on the basis of crystal structure data. These data can
be filled in a web form or they can be transferred as a CIF-file.

For the definition of rings and ring coverings see

* Goetzke, K., Klein, H.-J.: Properties and Efficient Algorithmic Determination of Different Classes
of Rings in Finite and Infinite Polyhedral Networks,
Journal of Non-Crystalline Solids, 127 (1991), 215-220*

or (in German)
**here **(PostScript, packed (gzip), 164KB) or
**here **(PostScript, unpacked, 2.6 MB).

Further references can be found at the homepage of H.-J. Klein

Some
**explanations on ring statistics** are helpful for interpreting the results.

Ring statistics for some structures can be found in

**rings** (ring classes and symmetry operations)

**node-cover** (minimal node covers)

**edge-cover** (minimal edge covers)

If you append SNUM (from statistics) to the address http://www.is.informatik.uni-kiel.de/~hjk/

(e.g.: http://www.is.informatik.uni-kiel.de/~hjk/b46.01.80)

you get the data of the corresponding structure.

The results of the algorithms are presented in textual as well as in graphical form
(VRML and Java applet). Graphical output can be modified interactively.

What you need is a HTML-Browser supporting Java 1.1 or higher
(e.g. **
Netscape Communicator 4.x**) and

a VRML Plug-in supporting
the External Authoring Interface (e.g.
**CosmoPlayer 2.1**).

There is a collection of
**examples**
allowing you to get an impression of the graphical interface of CRYSTANA.

For any comments or questions concerning the system feel free to contact

hjk@is.informatik.uni-kiel.de

Last modified: Tuesday, October 16th, 2012