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[Congress Report]

Open Commission Meeting on laboratory-based high-pressure crystallography

The Commission on High Pressure organized this meeting to focus on laboratory-based high-pressure science and techniques, and bring experts together with crystallographers keen to learn about the possibilities, limitations and essential equipment for starting or extending their laboratory-based activities. 3rd generation synchrotron sources have taken high-pressure crystallography into realms which before were inaccessible, and the question arises as to whether there is still relevant research to be done with in-house facilities. This meeting demonstrated that there is, not only in traditional single-crystal diffraction but also in powder diffraction, in extreme P and T regimes, and through application of non-diffraction techniques. D. R. Allan (Edinburgh U., UK) and R. Angel (Bayreuth U., Germany) summarized state-of-the-art single-crystal methods. David Allan demonstrated the determination of hydrogen locations with an off-theshelf diffractometer, and Ross Angel focused on the optimization of a diffractometer to obtain highly accurate cell parameters for equation- of-state measurements. J. Haines (CNRS, Meudon, France) explained the experimental set-up his group is using for powder diffraction with a standard sealed-tube source, and showed that such facilities are by no means limited to carrying out preparation for synchrotron experiments, but can support substantial leading-edge high-pressure research. L. Dubrovinsky (Uppsala U., Sweden) introduced the X-ray set-up of the Uppsala group, consisting of a rotating- anode generator and a SMART CCD-detector. With this very effective combination, experiments across the P-T range of the lower mantle are performed successfully in-house. An extended tea-break sponsored by Diacell Products, was followed by three talks focusing on non-diffraction techniques. J. D. Bass (Illinois U., USA) gave a lucid presentation of a basic set-up for high-pressure Brillouin scattering, and showed how it could be used as a powerful technique for determining sound velocities in minerals. M. Abd-Elmeguid (Cologne U., Germany) presented an overview of the essentials of highpressure Moessbauer techniques, and clearly defined the limits of what can be done with such an experiment. The meeting ended with an overview by K. Amaya (Osaka U., Japan) of the impressive techniques developed by his group to measure electric and magnetic properties of materials in the megabar range.

M. Kunz, Chair