During its third triennium, the Commission on Powder Diffraction has continued to be very active on a wide variety of fronts. Its major achievements have included the organization of three international round robin projects (one now complete), continuation of a series of workshops/schools on the Rietveld method, a journal publication, organization of several international meetings, continued support for a directory of powder diffraction programs, and expansion of its biannual Newsletter to include a mailing list of 850 powder diffractionists, translation of the Newsletter into the Chinese language, and its incorporation onto the World-Wide Web.
The CPD organized a satellite meeting entitled Advances in Powder Diffraction, SMP-93, in Hangzhou, China, 31 August-3 September 1993, immediately after the Beijing Congress. The main aim was to present recent developments in powder diffraction theory and practice and to emphasize the power of modern diffraction methods in materials science. A total of 140 delegates from 18 countries attended. The undoubted success of the meeting was due to the excellent efforts of Professor Ling Rong-Guo, Chairman of the Organizing Committee, and to CPD member J. I. Langford, Chairman of the Scientific Programme Committee, with much appreciated assistance from Professor Shen Shan-Hong, President of Hangzhou University, and Professor Lin Shao-Fan.
An International Workshop on Advanced Powder Diffraction Techniques in Mineral and Materials Processing was held in Pretoria, South Africa, in October 1994, and was co-organized by the Crystallographic Society and Mineralogical Association of South Africa. CPD member L. B. McCusker was an invited speaker and served as Chairman of the Scientific Programme Committee, member J. I. Langford was also an invited speaker, while CPD Chairman R. J. Hill contributed to the Programme Committee. The meeting was an outstanding success, with participants from many countries in southern Africa gaining valuable experience from a series of carefully crafted lectures, tutorials and hands-on workshop sessions on all aspects of powder diffraction analysis, including sessions presented by the ICDD.
An International Conference on Powder Diffraction and Crystal Chemistry was held in St Petersburg, Russia, in July 1994, co-organized by the Russian Association for Powder Crystallography, the Department of Crystallography of St Petersburg University, and the CPD. Lectures and posters were presented to 165 participants from 20 countries, including a workshop run by the ICDD, and a 211-page book of abstracts was produced. St Petersburg's strong past and current links with crystallography, dating from Federov's discovery of the 230 space groups in 1890, along with its geographic beauty, provided a very appropriate and delightful backdrop for a most successful conference.
After undertaking largely independent activities over the past six years, the CPD and the European powder diffraction community (in the form of the EPDIC series of meetings) started what is hoped to be an increasing level of cooperation. This interaction began with the invitation to the CPD Chairman, R. J. Hill, along with other members of the CPD, J. Fiala and D. Louër, to serve on the Programme Committee of the EPDIC IV meeting in Chester, UK, in July 1995. The collaboration will continue with similar CPD involvement in the organization of EPDIC V in Italy in 1997 and with assurances by the CPD and the ECC to coordinate their meetings in Europe so as to prevent overlap.
The CPD lent its support to the very successful International Meeting on Structure Solution from Powder Diffraction Data, held in Oxford, UK, in July 1995 and organized by W. I. F. David and colleagues from the Rutherford Laboratory, UK. CPD members D. E. Cox, L. B. McCusker, D. Louër and R. J. Hill presented invited lectures and workshops, and the IUCr provided a generous grant to the Organizing Committee. The conference was a very timely meeting with a productive mixture of lectures and workshops that captured much of the excitement of this rapidly evolving area of powder diffraction. A book is expected to evolve which will be a member of the IUCr Monograph Series.
The CPD was also involved in the International Conference on X-ray Powder Diffraction Analysis of Size/Strain, Macrostress and Texture held in Liptovsky Mikulas, Slovakia, in August 1995 under the local guidance of Dr P. Sutta. CPD members J. Fiala, J. I. Langford and D. Louër and Chairman R. J. Hill served on the Programme Committee, with J. Fiala as Chairman, and the IUCr again provided generous support in the form of a grant. The extended proceedings of this conference will be published shortly, with advice provided by the CPD.
CPD consultant and immediate past Chairman, R. A. Young, continued the series of CPD-organized three-day Rietveld Summer Schools with co-lecturers R. B. Von Dreele and A. K. Cheetham. The latest in this series was held in July 1995 at the Moscow State University, Russia, with Professor L. A. Aslanov as head of the local organizing group. The meeting was very well attended by 86 students and local scientists and, as usual, led to a significant enhancement of the participant's awareness of the capabilities of Rietveld analysis, particularly by young scientists. The CPD is once again grateful to the IUCr for providing financial support to assist with the travel expenses of the main lecturers and for registration and living-costs grants for students.
The CPD maintained a high profile in preparations for the Seattle Congress through the involvement of its Chairman, R. J. Hill, and member D. E. Cox on the Programme Committee and with associated responsibility for the coordination of lecturers and other contributions to most of the powder diffraction related microsymposia. The CPD's nominee, D. Louër, was invited by the IUCr to present a Plenary Lecture entitled Modern Powder Diffraction in Materials Science at the Congress, and the CPD-initiated microsymposium entitled Materials VIII - Powder Diffraction was also accepted, with R. J. Hill and J. B. Cohen (USA) as Co-Chairs.
In a novel initiative, the CPD combined forces with the 45th Annual Denver X-ray Conference (DXC) to organize jointly the Powder Diffraction Satellite Meeting in Denver, USA, 3-8 August 1996, associated with the Seattle Congress. Two members of the CPD, D. E. Cox and D. K. Smith, served on the Organizing Committee, and several CPD members and consultants were involved as invited speakers or workshop and special session organizers, including D. Louër (France), D. E. Cox (USA), R. J. Cernik (UK), H. Toraya (Japan), R. A. Young (USA) and R. J. Hill (Australia). In response to a joint request from the DXC and the CPD, the IUCr provided support for this ground-breaking meeting.
The CPD, through the Task Group Chairmanship of J. I. Langford, contributed to the development and acceptance of a powder diffraction dictionary for use in the CIF/STAR format for archival and transferral of crystallographic data. This CPD project was undertaken in collaboration with the ICDD through the leadership of now CPD consultant J. I. Langford and, representing the ICDD, B. Toby. The CPD was also involved in extended negotiations with the ICDD prior to acceptance of the CIF format for ICDD databases.
The CPD remained active in the execution of its existing projects and in the initiation of new ones. The results of Part II of the Rietveld Refinement Round Robin Project were published by Hill & Cranswick in J. Appl. Cryst. (1994), 27, 802-844. This concluding part of the project provided outcomes of the analysis of Rietveld refinements of the monoclinic zirconia crystal structure undertaken by 28 respondents using 27 X-ray and 14 neutron powder diffraction data sets collected on a `standard' sample with a wide spectrum of instruments located in 12 countries around the world. The results were used to provide an assessment of the performance (resolution) of various diffraction configurations and the relative merits of the data collection and structure refinement protocols used by respondents. These findings were used to define limiting factors for parameter accuracy and precision and to produce a series of `best practice' recommendations for the collection and analysis of powder data using the Rietveld method.
Continued organizational and financial support was provided by the CPD for the maintenance and updating of the World Directory of Powder Diffraction Programs, co-organized by S. Gorter (The Netherlands) and CPD member D. K. Smith. This compilation has now appeared in two updated versions and includes summary descriptions and contact information for several hundred programs. It has become a major resource that is available to the worldwide powder diffraction community. Two grants from the CPD have been used to enable the database to be even further expanded in scope and size, and to provide hardware for it to be distributed by anonymous FTP.
In conjunction with the Slovakia meeting, CPD member J. Fiala and R. L. Snyder (ICDD) co-chair a task group working on a Round Robin on Crystallite Size and Microstrain Determination. The preliminary results of studies on a widely circulated `standard' sample of a ceramic material containing inclusions of crystallites of known size were reported during the Slovakia meeting.
Two new projects were initiated in 1995. One involves the production of summary guidelines and protocols for the collection and analysis of powder data for Rietveld analysis and, related to this, the identification of a new Rietveld method `standard' material with higher complexity than the monoclinic zirconia sample used as a benchmark for the recently completed CPD Rietveld Refinement Round Robin Project. This work is being coordinated by CPD members L. B. McCusker and D. E. Cox. The second new project is being coordinated by D. K. Smith and R. J. Hill, and involves a new round robin survey of the accuracy, precision, capabilities and limitations of quantitative phase analysis by diffraction methods. The selection of appropriate multiphase samples and discussion of the protocols for the survey are well advanced, with the recommendations planned for open discussion during a workshop at the Denver Powder Diffraction Satellite Meeting in August 1996. The centre for distribution of survey materials and data analysis will be maintained by R. J. Hill and I. C. Madsen at Port Melbourne, Australia.
The CPD continued to produce two Newsletters per year during the triennium, with editorship rotated among the various members of the CPD. More than 850 copies are distributed to the current CPD mailing list, with a further 600 made available for pickup at various conferences and as part of other mailings. Feature articles have included the explanation, establishment and use of crystallographic newsgroups on the worldwide Internet (by L. Cranswick of CSIRO in Melbourne, Australia), use of synchrotron diffraction information from single powder grains for structure solution prior to Rietveld refinement using bulk powder diffraction data (by R. J. Cernik of Daresbury Laboratory, UK), description and use of CIF for powder diffraction (by B. Toby, Terrytown, USA), introduction to the SPring-8 project (by H. Toraya, Nagoya, Japan), the new high-resolution neutron powder diffractometer at the high-flux isotope reactor, Oak Ridge, USA (by B. Chakoumakos, Oak Ridge National Laboratory, USA), award of the Aminoff Prize to Hugo Rietveld (by R. Tellgren, Uppsala, Sweden), the contributions of Gunnar Hägg to powder diffraction (by S. Rundquist, Uppsala, Sweden), neutron powder diffraction at Kjeller (by Hauback, Fjellvåg and Steinsvell, Norway), a tribute to Arthur C. Wilson (by J. I. Langford, Birmingham, UK), and current powder diffraction activities at the Photon Factory (by H. Toraya, Nagoya, Japan).
CPD Member Professor Lin Shao-Fan of Nankai University, China, arranged for Newsletter No. 10 to be translated into Chinese and for it to be distributed, along with a translation of the journal Powder Diffraction, to 300 powder diffractionists in China. This process will be continued for the foreseeable future and will significantly expand the number of people exposed to the CPD by more than 500 persons.
An innovative feature of the CPD Newsletter's availability now and in the future is its recent installation on the World-Wide Web with access via a pointer from the IUCr Home Page. CPD member R. J. Cernik (Daresbury Laboratory, UK) has installed a copy of Newsletter No. 15 along with contact details and a brief introduction to the CPD and has agreed to continue this service for subsequent issues. It is expected that this innovation will ultimately provide even more widespread access and contributions to the activities of the CPD during the next triennium. The CPD is grateful to the Daresbury Laboratory for its agreement to support the distribution of the Newsletter in both hard and soft form in this manner.
The CPD continued its strong interaction with the International Centre for Diffraction Data through the representation of several of its members on ICDD Subcommittees and the election of others to ICDD membership. In particular, CPD Secretary, D. Louër (France), is Chairman of the ICDD Data Collection and Analysis Sub-committee and Consultant to the Board of Directors, while CPD members J. Fiala (Czech Republic) and H. Toraya (Japan) were elected members of the ICDD during 1993. The CPD Chairman, R. J. Hill (Australia), is ex officio IUCr representative to the ICDD, and Dr L. K. Frevel (USA), Distinguished Fellow of the ICDD, is their representative to the CPD.
1 February 1996 R. J. HILL, Chairman
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