W0117

Microcrystal Diffraction Studies at ESRF and GSECARS at the APS. J.J. Pluth, M.L. Rivers, S.R. Sutton and P.J. Eng, Dept. of Geophysical Sciences, CARS and MRSEC, The University of Chicago, Chicago, IL 60637 USA

With the increased brilliance of third generation synchrotron sources, it is now possible to solve crystal structures of materials usually classified as polycrystalline or powder samples. In fact, a high quality crystal structure refinement has already been completed using a single crystal of kaolinite with 8 µm³ volume on ID13 at ESRF [1].

Technological problems that must be solved before this kind of experiment becomes routine, include the selection and isolation of a tiny single crystal and transfer to a fiber of dimensions comparable to the crystal. Optical microscopes equipped with micromanipulators, developed for biotechnology applications, can be used for this task. Pipette pullers, also used in biotechnology, can provide stable 0.2 µm mounting tips. Submicron single crystals been successfully mounted using a micromanipulator installed within a scanning electron microscope [2].

Our exploratory studies at beamline ID13 at ESRF were successful in that it was possible to mount, record single crystal diffraction data and to solve unknown crystal structures of samples with volumes as small as 125 µm³. A particularly important result of these studies was the determination of the crystal structure of a mineral raite using a 3x3x65 µm³ crystal [3]. Using a laboratory source, we have successfully determined the structure using a choloalite crystal (a high-Z mineral) of approximately 8000 µm³.

We are currently developing a multiuse diffraction beamline at GeoSoilEnviroCARS at the APS. The beamline is being built on an undulator and for microcrystallography applications it will eventually be configured with a cryogenically cooled monochromator and both vertical and horizontal focusing 1 m mirrors. We will soon be taking delivery of a large Newport 6-axis [kappa]-diffractometer, which will be coupled with a Bruker 2K CCD detector using the SMART system software. Initial experiments will be completed using an in hutch channel cut Si monochromator and two (vertical and horizontal focusing) 10 cm Kirkpatrick-Baez mirrors. Using the APS source these mirrors have already delivered a 1.3x4 µm² beam.

[1] Neder RB, Burghammer M, Grasl T, Schulz H, Bram A, Fiedler S, Riekel C, Z. Kristallogr. 211 (1996) 763-765. [2] Neder RB, Burghammer M, Grasl T, Schulz H, Z. Kristallogr. 211 (1996) 365-367. [3] Pluth JJ, Smith JV, Pushcharovsky DY, Semenov EI, Bram A, Riekel C, Weber HP, Broach RW, Proc. Natl. Acad. Sci. USA 94 (1997) 12263-12267.