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IUCr 1993 Triennial Report - Commission on Powder Diffraction

During the triennium, the CPD was actively involved in various projects, meetings and Workshops/Schools and in planning for future ones.


The CPD project to produce a book on the subject came to fruition with the publication of The Rietveld Method in early 1993 by the Oxford University Press as No. 5 in the series IUCr Monographs on Crystallography.

The Proceedings of the International Conference on Accuracy in Powder Diffraction II (see below), held 26-29 May 1992, were published as NIST Special Publication No. 846 at the end of 1992. The editors, E. Prince and J. K. Stalick, are due special congratulations and appreciation for getting the Proceedings out in good form and substance in such a remarkably short time.

The results of the first phase of the Rietveld Refinement Round Robin (RRRR) were published: Hill (1992). J. Appl. Cryst. 25, 589-611.

The project of establishing a Program Information Exchange Bank on computer programs for powder diffraction data analysis has been conducted by D. K. Smith, Consultant to the CPD. The first phase of this project came to fruition with the publication of a categorized and annotated list of more than 280 programs, with informative discussion of each category, in J. Appl. Cryst. (1991), 24, 369-402, authored by D. K. Smith and S. Gorter and reviewed before publication by the entire CPD membership.

The intended two-per-year schedule for producing CPD Newsletters was kept: Nos. 4 and 5 were published in 1990, 6 and 7 in 1991, and 8 and 9 in 1992. More than 1000 copies of each of the later issues were distributed. A conscious effort to increase the Newsletter mailing list of interested persons has met with some success. A check of the mailing list against the current World Directory of Crystallographers (WDC) verified that our Newsletters reach a community not well represented in mainline crystallography: approximately one half of the names on our mailing list are not in the current WDC.


A Satellite Meeting on Powder Diffraction, originated by the CPD, took place in Toulouse on 16-19 July 1991. The Programme Committee was chaired by D. Louër (Rennes) and the Organizing Committee by J. Galy (Toulouse). That these Committees did outstanding jobs was attested by the facts that there were 255 scientific registrants and that enthusiasm remained high throughout the meeting. The scientific sessions were held in an air-conditioned auditorium at the Paul Sabatier University (Université de Toulouse II) and the large lobby area (also air-conditioned) just outside it was filled mainly with posters but also provided `coffee', social, and registration areas. The social events included a reception at City Hall in the lush `Salle Illustrée', a laboratory visit and reception with free-flowing liquids at Dr Galy's Centre d'Optique Electronique, and a chartered bus ride to Bordeaux marked by camaraderie and a box lunch.

At the Bordeaux Congress, two of the Microsymposia were engendered by the CPD, those on Advances in Structure Determination from Powder Diffraction Data (A. K. Cheetham and D. Louër) and on Powder Diffraction Studies of Fibrous, Polymeric and Similarly Imperfectly Ordered Materials (K. H. Gardner, D. Tchoubar and R. A. Young). Both session topics attracted a number of posters and a substantial and very interested audience.

The CPD also participated in the trial of a new feature for the International Congresses of Crystallography: Discussion sessions organized `on-the-spot', or nearly so, in each of which the topic is to be the posters associated with one or two particular Microsymposia. Such a discussion session on the posters associated with the above-mentioned Microsymposia was organized, on behalf of the CPD, and moderated by R. J. Hill. The vigour of the discussions indicated that this new feature might well become a standard feature of our Congresses.

A major inter-Congress meeting was held 26-29 May 1992 at the National Institute of Standards and Technology in Gaithersburg, MD, USA, with the title Accuracy in Powder Diffraction II (APD-II). There were 175 registered participants from 18 countries. The meeting was organized by the CPD and was sponsored by the ICDD, the IUCr and NIST. Generous financial support for speakers and young scientists was received from the ICDD and the IUCr, respectively. Excellent local arrangements were made under the Co-chairmanship of E. Prince and J. Stalick of NIST. The Programme Chairman was R. J. Hill (Australia), who is also Secretary of the CPD. The participants seemed to be very satisfied with the meeting.

Four three-day Rietveld Summer Schools were organized by the CPD during the triennium: August 1990 and 1992 at the Silesian University in Cieszyn, Poland, with Z. Bojarski as head of the local organizing group; 8-10 December 1992 at the National University in La Plata, Argentina, with G. Punte leading the local organizing group; and 14-16 December 1992 at the University of São Paulo at São Paulo, with Y. Mascarenhas and L. Amaral in charge of the local organization. The Schools featured hands-on practice on PC-type computers. Student attendance ranged from 30 to 58 and was limited primarily by the number of computers available. For the two Schools in Poland, financial support was provided by the IUCr for the travel of the main lecturers (A. K. Cheetham, R. B. Von Dreele and R. A. Young) and for registration and living-costs grants for 20 students from various European countries. The December Schools received financial sponsorship from CONICET (Argentina) and CNPQ (Brazil). The full travel expenses of the three lecturers from the northern hemisphere were funded by the Cooperative Science programs that the US NSF has with CONICET and CNPQ. The Schools were also sponsored in name and underwritten by the IUCr through its Visiting Professorship Programme and Commission on Crystallographic Teaching. Although in the end no IUCr money was used, the IUCr's underwriting was crucial; the Schools could not have been held without it. The reason is that the NSF funding, welcome though it was, did not actually come through until after all plans and local arrangements, including local financial commitments, had been made, travel tickets had been bought and one of the lecturers had already boarded his plane.

The CPD co-organized the International Workshop of Crystallography: Computational Methods in X-ray Powder Diffraction Analysis held in Aswan, Egypt, 16-26 January 1993. Three CPD members served on the Programme Committee, one as Chairman. Funding to bring in all the needed topic-organizing Chairmen fell short. Much appreciated was the fact that the IUCr's Visiting Professorship Programme provided travel funds for D. K. Smith to give an intensive five-day course on Mineralogical Crystallography at Ain Shams University in Cairo after the Workshop. That made it possible for him to organize and conduct one of the most important teaching sections of the Workshop, that on quantitative phase analysis by diffraction means. Also placed on the teaching programme were F. R. Ahmed (NRC, Ottawa), A. Authier (IUCr President, Paris), S. Gorter (Delft), R. Jenkins (ICDD), S. E. Rasmussen (Aarhus), J. Schneider (Munich), H. Toraya (Nagoya), G. Will (Bonn), A. Wright (Reading) and CPD members J. I. Langford and D. Louër, who also served on the Programme Committee.

The Satellite Meeting on Powder Diffraction to be held in Hangzhou, China, 31 August-3 September 1993 was initiated and is being co-organized by the CPD. The Programme Committee, under the able Chairmanship of CPD member J. I. Langford, did most of its work during this reporting period. In response to a request from the CPD, the ICDD has allocated US$5000 in support of this meeting.

Other Projects

A Task Group on Crystallite Size and Microstrain Determination has been set up jointly with the ICDD. J. Fiala (CPD) and R. L. Snyder (ICDD) are the Co-chairs. The first focus is to be a round robin, which will illuminate the current methodologies and data-interpretation models used by the participants, including strengths and weaknesses of the methods and models.

The CIF/STAR format, previously recommended by the CPD to be extended for use with powder data, has now been accepted by the ICDD. J. I. Langford chairs the CPD's development efforts and coordinates with B. Toby who chairs the ICDD's.

Phase two of the Round Robin on Rietveld Refinement is nearing completion. In mid-1993, the results will be submitted for publication in the Journal of Applied Crystallography. This large project is being coordinated by R. J. Hill (CPD Secretary). It is an intercomparison of 41 X-ray and neutron powder diffraction sets collected on a standard sample of monoclinic zirconia using 31 different instruments in 18 countries. The results should prove to be even more interesting than those arising from Part I of the project. Dr Hill is scheduled to present a short summary of them at the 1993 Satellite Meeting on Powder Diffraction in Hangzhou.

The ICDD's Hanawalt Award was presented to CPD member D. Louër during the opening ceremonies of the EPDIC-2 meeting in Enschede, The Netherlands. It is given for excellence in the field of powder diffraction.

23 April 1993                                R. A. YOUNG, Chairman

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