Open Commission Meeting: Technical developments in high-pressure crystallography

The OCM “Technical Developments in High-pressure Crystallography” organized by the IUCr Commission on High Pressure took place on afternoon August 29, immediately after the six regular microsymposia devoted to the various fields of high-pressure crystallography. Together with the OCM “Single Crystal Studies under High Pressure” it attracted an excellent audience of about 50 participants. The OCM covered all technical methods – from classical diffraction to inelastic scattering - which are used by high-pressure crystallographers. The recent developments in X-ray diffraction on third-generation X-ray sources had been presented in the talks of M. Mezouar (ESRF, France), T. Katsura (Okayama University, Japan) and J. Zaug (Livermore Nat. Lab., USA). The ID30 beamline at the ESRF was the first specialized high-pressure beamline installed at a third-generation synchrotron source and had shown an impressive performance for about a decade. In 2005, this activity was moved to another beamline, ID27. In his talk, Dr. Mezouar convinced the audience that the new beamline provides even more opportunities for the high-pressure community than the famous ID30, including an increase in intensity by almost two orders of magnitude and separated hatches for large-volume and diamond anvil cells. The large-volume studies were the main subject of the next speaker, Dr. T. Katsura. The new press installed at the Spring-8 synchrotron source in Japan provides new opportunities for geophysical studies and material synthesis in the pressure range (above 50 GPa) exceeding the previous limits for this technique. Everyone working with powder diffraction at a synchrotron source knows that the powder averaging could be a problem – which could be greatly reduced by rotating of the sample during the measurement. Nevertheless, it was hard to imagine that the many-tons press could be rotated on a synchrotron beam with a micron precision, as Dr. T. Katsura had shown in his talk. The diffraction techniques were also covered in the talk of Dr. J. Zaug who had described a new specialized beam line at the ALS source in USA. Undoubtedly, this talk is of great interest for anybody planning high-pressure developments on forthcoming medium-energy sources, such as the DIAMOND in U.K. and the Soleil in France. Another specialized high-pressure facility, the HP-CAT beamline (described by Dr. O. Degtyareva from the Geophysical Laboratory, USA) is an impressive cocktail of different techniques which includes classical diffractions, inelastic scattering, near-absorption-edge measurements and nuclear forward scattering. The beamline is installed at the APS source in USA and, as Dr. Degtyareva had shown in her talk, produces excellent results in various areas of fundamental physics, geophysics and chemistry. In more details, the inelastic X-ray scattering had been discussed in the talk of Dr J.-P. Rueff (University Paris VI, France) who described recent progress in studies of magnetic properties under pressure at the ESRF. Despite difficult mathematical background required by this technique, these measurements manifest important changes in magnetic properties of various oxides under pressure. Finally, the audience had benefited from an exhibition organized by several companies providing equipments and tools for high-pressure research.

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