The Commission has continued to be active in the promotion of Aperiodic Crystallography as well as in coordinating activities between the quasi-crystalline and incommensurate structure communities.

As part of these activities, the Commission continued to promote Aperiodic crystallography at national, regional and international meetings. During 2005, the triennial Congress of the IUCr, IUCr XX, was held in Florence and Aperiodic Crystallography was again strongly represented. Prior to the opening of the Conference itself, a full day, pre conference Workshop (WK04) on the Structural Analysis of Aperiodic Crystals was held. The Workshop was organized under the auspices of the Aperiodic Commission by Sander van Smaalen and Ray Withers (see the attached report of this Workshop for more details). During the Congress itself, two Keynote lectures on Aperiodic Crystallography, "Structure analysis of Modulated Crystals: Trends and Tendencies" by Vaclav Petricek and "Quasicrystal Structure Analysis. The State of the Art" by Akiji Yamamoto were presented in well-attended sessions. In addition, three separate Microsymposia, MS19, "News from Incommensurate Crystals", MS26, "Recent Advances in Quasicrystal Research" and MS 83 "Computational Solutions for Aperiodic Crystals" were also held and again were well supported.

In addition to the activities associated with IUCr XX, a well attended microsymposium on "Crystal chemistry and complex superstructures" co organized by Sander van Smaalen was held during the German Crystallographic Association meeting held in Cologne, Germany from February 28 to March 4, 2005 while a microsymposium on "Disordered and Modulated Materials" was held during Crystal 24, the 24th meeting of the Society of Crystallographers in Australia and New Zealand (SCANZ), held at Marysville near Melbourne from March 29 April 1, 2005.

The most important upcoming meeting for the Commission is Aperiodic 2006 to be held in Zao (near Sendai), Japan from 17-22 September 2006. The meeting is organized by A. Yamamoto (Chair), An Pang Tsai (Vice-Chair), Y. Gotoh, Y. Michiue, Y. Miyazaki and K. Saitoh and is shaping up to be a very exiting meeting. Other up-coming activities include the 5th Workshop on the Structural Analysis of Aperiodic Crystals organized by Sander van Smaalen to be held in March 2007 at the University of Bayreuth in Germany. A meeting on Quasicrystals to be organized by Ron Lifshitz is also planned for Israel in 2007.

The Commission maintains internet pages at the web site of the IUCr at http://www.iucr.org/iucr-top/comm/capd/index.html. A web site on all aspects of the crystallography of aperiodic crystals is maintained by the special interest group (SIG) on aperiodic crystals of the European Crystallographic Association. It is maintained by M. Dusek (Prague, Czech Republic), and it can be found at http://www-xray.fzu.cz/sgip/aphome.html.

Ray Withers,
Chair of the Commission on Aperiodic Crystals of the IUCr.