Journal
JOURNAL OF APPLIED CRYSTALLOGRAPHY
Volume 38, Issue -, Pages 757-759Publisher
WILEY-BLACKWELL
DOI: 10.1107/S0021889805023344
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The Rietveld method of crystal structure refinement was an important breakthrough, allowing crystal structural information to be obtained from powder diffraction data. One remaining challenge is to collect Rietveld-quality data for polycrystalline minerals in situ, using laboratory-based micro X-ray diffraction (mu XRD) techniques. Here a new data collection method is presented, called 'multiframes', which produces high-quality data, suitable for Rietveld refinement, using the Bruker D8 DISCOVER micro X-ray diffractometer. 91 frames of two-dimensional X-ray diffraction data were collected for powdered NIST SRM 660 LaB6 standard material, using a general area-detector diffraction system (GADDS), at intervals of 0.8 degrees 2 theta. For each frame, only the central 1 degrees 2 theta was integrated and merged to produce a diffraction profile from 17 to 90 degrees 2 theta. Rietveld refinement of this data using TOPAS2 gave a unit-cell parameter (a(o)) and atomic position of boron (x) for LaB6 of 4.1549 (1) angstrom and 0.1991 (9), respectively (R-wp = 4.26, R-Bragg = 3.21). The corresponding La - B bond length was calculated to be 3.0522 angstrom. These parameters are in good agreement with the literature values for LaB6. These encouraging results suggest that Rietveld-quality micro X-ray diffraction data can be collected from the Bruker D8 DISCOVER diffractometer, provided that the GADDS detector is stepped in small increments, for each frame only the central 1 degrees 2 theta is integrated at constant arc length, and counting time is sufficient to yield adequate intensity (similar to 10 000 counts).
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