ITAP Homepage
Dr. Franz Gähler

Institut für Theoretische und Angewandte Physik
Universität Stuttgart, Pfaffenwaldring 57/VI, 70550 Stuttgart

Phone +49 711 685-65260;  Fax +49 711 685-65271
Email: gaehler@itap.physik.uni-stuttgart.de

IMD - The ITAP Molecular Dynamics Program

I am coordinating the developement and maintainance of IMD, a molecular dynamics program designed to run efficiently on both simple workstations and massively parallel supercomputers. IMD is easily portable; its parallel version communicates via the standard Message Passing Interface (MPI). IMD supports a large number of thermodynamic ensembles and simulation options. It is continuously being developed and extended.

Computing With Crystallographic Groups

Crystallographic groups describe the symmetry not only of crystals, but also of quasicrystals. However, unlike for crystalline space groups, there are no International Tables for quasicrystalline space groups. For this reason, I have written (with Bettina Eick and Werner Nickel) programs that allow to determine the space groups of arbitrary dimension, and to perform various kinds computations with them. These programs are available in the package Cryst built on top of the computer algebra system GAP. Cryst has already been used to check the data of the upcoming volume on maximal subgroups of space groups of the International Tables, and to compute cohomology groups of spaces of quasiperiodic tilings. Complementing the package Cryst, there are two further GAP packages for the computation with crystallographic groups. The package CrystCat makes a catalogue of all crystallographic groups up to dimension 4 available to Cryst, and Carat provides a GAP interface to CARAT, another package of programs for the computation with crystallographic groups, developed at Lehrstuhl B für Mathematik, RTWH Aachen.

Cluster Models for the Stabilization of Quasicrystals

Cluster density maximization principles represent an attractive way to explain the existence and stability of quasicrystals. Such principles have successfully been applied to octagonal, decagonal, and dodecagonal quasicrystals. There is also a recent review article.

Quasiperiodic Tilings

Quasiperiodic tilings serve as simple models for the structure of quasicrystals. Besides their usefulness, they also have an artistic aspect. Here are some nicely colored examples, either as GIF bitmaps or in PostScript.

List of Publications

Many of the articles in my list of publications are available here (in gzipped PostScript).