W0026

Diffraction Experiments on Submicrometer Sized Single Crystals. R.B.Neder, Institut für Mineralogie, Uni-Würzburg, Am Hubland, 97074 Würzburg, Germany

A method to prepare micrometer sized crystals for a diffraction experiment will be presented together with results that include hydrogen positions. The successfull range of single crystal diffraction has been expanded into the submicrometer range.

A manipulator has been developed for use inside a SEM. The manipulator uses a combination of mechanical translations operated by stepper motors with piezo drives that allow movements on a nanometer scale. The manipulator fits into the sample chamber of a Zeiss DSM960 SEM. By using this equipment individual single crystals of size down to a few hundred nanometers can be mounted onto thin glas fibers. These glas fibers have been specially tailored to a diameter of one micron.

Diffraction experiments have been performed on different kaolinite single crystals at the microfocus beamline ID13, ESRF. The structure refinements on very well ordered samples from Keokuk, Iowa show exceptional structural detail. The space group, long contested, can unambiguously be assigned and the structure fully be refined including the hydrogen positions.

Single crystals of an extremely disordered kaolinite from Georgia, show an intricate pattern of diffuse scattering with so far unknown detail.

References

Neder, R.B., Burghammer, M., Grasl, T. & Schulz, H.: Mounting an individual submicrometer sized single crystal. Z. Kristallogr. 211 (1996) 365-367.

Neder, R.B., Burghammer, M., Grasl, Th., Schulz, H., Bram, A., Fiedler, S. & Riekel, Ch.: Single crystal diffraction by sub micrometer sized kaolinite; observation of Bragg reflections and diffuse scattering. Z. Kristallogr. 211 (1996) 763-765.