In 1999 the Commission on Aperiodic Crystals met during the XVIII IUCr Meeting in August 1999 in Glasgow. The activities were discussed. The general assembly reappointed the Commission with several old and new members.

Following previous work, the CIF dictionary for modulated structures was completed, and it was submitted for approval to the Committee for the Maintenance of the CIF Standard. Based on this new CIF dictionary a database of incommensurately modulated structures and composite crystals was developed. Both projects evolved under the direction of G. Madariaga (Bilbao). The CIF standard and the database are available at the Bilbao Crystallography Server at http://www.cryst.ehu.es/icsdb/index.html.

The Commission was involved with the preparation of Aperiodic 2000, which continues a series of triennial meetings on aperiodic crystals. This conference will take place from 4 to 8 July 2000 in Nijmegen, The Netherlands, and it is organised by T. Janssen. Aperiodic 2000 brings together scientists working on quasicrystals, incommensurately modulated structures, composite crystals, and polytypes. Information on this meeting can be found at the web site http://www-sci.sci.kun.nl/tvs/aperiodic/.

The Commission continued to promote activities on the crystallography of aperiodic crystals at national and international meetings. Two microsymposia were organised at the XVIII IUCr Meeting in Glasgow (August 1999). One was concentrated on structural aspects of aperiodic crystals, and the other was concerned with theoretical crystallography and symmetry aspects of aperiodic crystals. A satellite meeting to the International Congress on Quasicrystals was organised by W. Steurer (Zurich) on the subject "Quasicrystal Structure Analysis" (24-25 September 1999 in Stuttgart, Germany).

A workshop on the Structural Analysis of Aperiodic Crystals took place in Bayreuth on 5 and 6 March 1999, and it was organised by S. van Smaalen. In addition to a series of lectures, the participants could study the crystallography of incommensurately modulated structures and composite crystals using a script on a series of worked-out examples. The participants were encouraged to recreate these examples using the computer program JANA.

The web site of the special interest group on aperiodic crystals of the European Crystallography Association was extended. It contains extensive information on many aspects of the crystallography of aperiodic crystals (e.g. a list of computer programs). It is maintained by M. Dusek (Prague), and it can be found at http://www-xray.fzu.cz/sgip/aphome.html. The web site of the Commission on Aperiodic Crystals of the IUCr is at http://www.iucr.org/iucr-top/comm/capd/index.html.

Bayreuth, 29 February 2000

Sander van Smaalen

Updated 17 July 2000