Dear mailing list, Would anyone be able to help me with a problem I am having refining some data using TOPAS on a lab X-ray pattern? The diffraction patterns collected show a large amount of asymmetry in the first couple of (low angle) peaks. The diffractometer contribution to the profile was determined from refinement of a quartz standard and the sample dependent broadening was then modelled using the PV-II function within TOPAS. Axial convergence parameters were used to model the angle-dependent asymmetry. Unfortunately the asymmetry of the first, lowest angle peak is still being fitted very poorly. Are there any other parameters or tricks that will help to model this asymmetry? Many thanks for any help you have, Alex P.S. Additionally, the data was collected using a Bruker D8 Advantix diffractometer in capillary geometry, with a Cu source, a Ge(111) monochromator, secondary soller slits (2.5 degrees) and an linear PSD. _________________________________________________________________
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