The High Resolution Powder Diffraction beamline ID31 at the ESRF

Michela Brunelli

ESRF, Grenoble, France

Powder diffraction is an important and often unique crystallographic tool to determine the structures of polycrystalline materials in powder crystallography, for measurement of residual strain in bulk materials, in in-situ measurements for the exploration of phase diagrams with temperature, pressure, the kinetics of chemical reactions, following the changes in the crystalline components in electrochemical cells with charging and discharging, etc. One of the major general strengths of powder diffraction is the ability to carry out measurements under a wide range of conditions. At the High Resolution Powder Diffraction beamline ID31 at the ESRF, ancillary equipment is available for experiments in a wide range of temperatures, from room temperature down to 2.5 K using either a cold nitrogen gas blower or a liquid-helium-cooled cryostat; or at high temperature, up to 900ºC, using a hot air blower. Higher temperature can be reached using a parabolic mirror furnace, using halogen lamps; in this case the sample has to be contained in platinum capillary and it can be heated to ~1500ºC. An in-situ gas-handling system has been necessary to allow volatile compounds to be condensed in a capillary mounted on the axis of the diffractometer for standard powder X-ray diffraction studies. This gas-handling cell has also been employed in in-situ experiment that required fluxing gas through the sample during data collection, at modest pressures (up to 20 bar).

More recently, systematic pH- and temperature variations of crystallization conditions of relatively small protein were monitored using high-resolution powder diffraction data. Structural modifications of polycrystalline hen egg-white lysozymes (HEWL), precipitated in the pH range between 6.56 and 3.33, at 4ºC and at room temperature (for a total of 48 samples) were revealed from X-ray powder diffraction data. The experiment was also possible thanks to the automation in data collection achieved by employing robotic equipment for sample change.

In this presentation, a general overview of the diverse research activities carried out at the High Resolution Powder Diffraction beamline ID31 at the ESRF, in Grenoble (France), will be given.