IUCr 1996 Report - Commission on Powder Diffraction

The Commission was extremely busy in 1996 with the main Seattle Congress and the combined powder diffraction satellite and XRD/XRF conference at Denver. The Commission played a major role in both events in addition to its already very ambitious programme of size/strain, quantitative analysis and Rietveld refinement evaluation. The mailing list for the Commission Newsletter continues to grow and a new home page on the World Wide Web (http://www.dl.ac.uk/SRS/XRD/IUCR/) has been established. The twice-yearly CPD Newsletter reaches a substantially different audience to the main IUCr Newsletter and as such will continue for the next triennium. The CPD plans to make this information available in electronic form for as wide an audience as possible.

Meetings/Workshops/Schools

The preparations for the Denver and Seattle meetings dominated the first half of the year. The Commission was involved directly with sessions on materials research using powder diffraction and structure determination techniques. The Commission was represented on the main Programme Committee by D. Cox and R. J. Hill. At the combined IUCr satellite and Denver conference the Commission organized sessions on peak profile analysis, precision and accuracy in structure refinement from powder data and phase quantification. The CPD was represented on the Denver Programme Committee by D. K. Smith and D. Cox. This was in addition to participation by individual members in a large number of other microsymposia. The sessions were so well attended in Seattle that extra seats had to be provided in the lecture theatre. The CPD sessions at Denver were also very successful providing a good balance between the academic and industrial research that characterizes the Denver meetings. Professor D. Louër (Rennes, France) gave the keynote lecture at the Seattle Congress entitled Modern Powder Diffraction in Materials Science. This was an excellent talk covering all aspects of powder diffraction with particular emphasis on its applications. Professor Louër pointed out just how far the subject has progressed in ten years since the CPD was formed.

The Commission has been involved in the European powder diffraction meeting in Parma (EPDIC 5) through the Programme Committee (R. J. Cernik and P. Scardi) and by recommending IUCr support for students. The general relationship between the EPDIC meetings and the IUCr is becoming clearer after some discussion. The EPDIC meetings are very successful in their own right and will continue to be independent meetings. They will still attract IUCr support and the CPD will continue to look for informal ways to encourage cooperation. The EPDIC meetings will as far as possible be held 14 to 15 months apart with a break of one year during the IUCr main congress years. The CPD hopes that powder diffraction will play an increasing role in the ECM and that the current excellent relationship with EPDIC will continue. In addition to these major meetings, the Commission lent its support to the 5th School on X-ray Diffraction from Polycrystalline Materials, Frascati, Italy. The subject of the school was glancing-angle X-ray diffraction. There was also a powder diffraction course in Merida, Venezuela, and a meeting on materials structure characterization in the Czech Republic.

Projects

The CPD has continued to help the development of the Program Exchange Bank (PEB) for powder diffraction software and has provided a platform for the launch of an anonymous ftp site. The project to evaluate quantitative phase analysis is being led by R. J. Hill and D. K. Smith; this is at the stage of calling for interested parties to participate in the programme. The Commission is following up the Rietveld refinement comparison study published by Hill et al. in 1994 with a set of recommendations. This is being led by L. B. McCusker and R. Von Dreele and will probably appear in one of the IUCr journals this year. The CPD is also actively searching for new standard materials with more refineable parameters for more complex Rietveld comparisons. Retired CPD member D. Cox has agreed to continue with this project. Later this year, the Commission wishes to conduct a survey of instrumentation to determine the need for laboratory-based high-resolution studies.

Newsletters

Two Newsletters were produced in 1996, issue 16 was edited by V. Valvoda (Prague) and issue 17 by L. B. McCusker (Zürich). The first of these contained a detailed account of powder diffraction in Prague in an imaginative style. The work described covered a wide field and included multilayers, thin films, texture, distortions, minerals, ceramic superconductors and aerosols. The latter Newsletter contains a feature article on powder diffraction at the ESRF by A. Fitch; the benefits of a small source size are becoming very clear. The announcement for expressions of interest in the Quantitative Phase Analysis programme was published along with a very comprehensive series of meetings reports. These covered the Venezuelan, Italian and Czech meetings described earlier as well as session descriptions from Denver and Seattle. Reports on the Denver meeting from R. J. Hill, H. Toraya, D. Cox and R. A. Young described diffraction peak profile analysis, phase quantification, detector development, thin films and accuracy in powder diffraction. Seattle reports from R. J. Cernik, R. J. Hill and R. Tellgren described D. Louër's keynote lecture and the sessions on materials (VIII) and structure determination from powder data. Both Newsletters give up-to-date contact points and meetings calendars and provide a vital platform for information exchange throughout this very lively Commission.

Collaboration with other Commissions

With the expansion of the number of IUCr Commissions, the CPD wishes to form new links with other Commissions in order to promote new areas of cooperation. The CPD hopes to form strong links with the Commissions for High Pressure, Electron Diffraction, Neutron Scattering, XAFS, Small-Angle Scattering and Synchrotron Radiation. At present, these collaborations are at a very early stage although there are some very promising avenues such as structural characterization with electron crystallography followed by Rietveld structure refinement. The Commission is actively pursuing the possibilities for scientific cooperation as well as ideas for shared meeting sessions.

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