1999 Report in Acta Cryst, ????, 2000
Commission on Charge, Spin and Momentum Densities

The Commission promotes the study of electron density distributions in both real and momentum space by bringing together physicists, chemists and crystallographers in conferences, workshops and schools and by initiating and carrying out projects. Up to date information on the activities of the Commission are placed on the Commission's web page, accessible via the IUCr web pages (http://www.iucr.ac.uk/iucr-top/comm/csmd/index.html).

Meetings of the Commission

The Commission held open and closed meetings during the 18th IUCr Congress and General Assembly in Glasgow, August 1999. Discussion centred on the forthcoming Sagamore Conference (September 2000 in Poland) and the progress of the projects.

Conferences

18th IUCr Congress and General Assembly in Glasgow, August 1999 In addition to a Key Lecture by Yu Wang (Taiwan), two microsymposia were directly relevant to the Commission's interests: 6C - Chemical Insights from Charge Density Analysis. The idea for this microsymposium arose from the recognition that a great deal of chemically meaningful information is now being derived from careful charge density studies of x-ray data. However, in many instances, this is not being conveyed to the wider chemical community. The invited speakers were asked to focus, as much as possible, on the chemical outcomes of their studies. 9D - Synchrotrons and Charge Density Analysis. The increasing use of synchrotrons for collection of precision diffraction data for charge density analysis indicated that a session devoted to just these studies would be timely. Both microsymposia proved to be extremely popular, with lecture halls filled to capacity, and feedback indicates that they were very well received by charge density practitioners as well as the wider chemical community. Nearly fifty poster presentations were also made in topics related to these microsymposia.

2nd European Charge Density Meeting, Sitges, Spain, September 1999 These meetings fill the gap between the Sagamore and Gordon conferences on charge, momentum and spin densities. ECDMs are growing, both in attendees (more than 70 on this occasion) and interest, and they are being established as a new meeting point between the other two conferences. Scientific sessions were devoted to three main subjects: Intermolecular Interactions; Modelling Spin and Momentum densities; X-ray diffraction under external perturbations. The organizers tried to cover much of the charge, momentum and spin density community, and theorists and experimentalists were involved together in both sessions and discussions. The next ECDM will be organized by Finn Larsen in Denmark.

Sagamore XIII, Stare Jablonki, Poland, September 2000 . Plans are well underway for this meeting, which is held under the auspices of the Commission. Sessions will cover: charge density distributions; spin density distributions; electron momentum density distributions; theory: state-of-the art of the electronic wave functions and electronic structure of matter; instrumentation and data treatment, new instruments and measuring methods; multipole expansions, Fourier series - related techniques, maximum entropy and related methods; complementary techniques such as positron annihilation, Mössbauer effect, NMR, NQR, µSR and deep inelastic neutron scattering.

Projects

Five projects have been supported in recent years by the Commission, and the Glasgow meetings of the Commission elicited some vigorous debate on their continuation. Projects on Density Matrices (W. Weyrich) and Fermiology (A. Bansil) have been active for some time, and it may be timely to discontinue these as Commission projects. The Maximum Entropy project (M. Sakata) is still active, and current details can be found at http://www.mcr.nuap.nagoya-u.ac.jp/mem/index.html. The project on Multipole Refinement (C. Lecomte) is in progress, with analyses completed of both experimental and theoretical data for corundum. The other Commission project, on developing a Multipole Refinement Program (T. Koritsansky) has essentially been completed. XD now has over 70 subscribers worldwide, and has quickly become the package of choice for multipole refinement and subsequent estimation of properties based on the charge distribution.


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