Dear Rietveld Friends. I allowed myself to attach DOC files with 3 models where I'm trying to provide Rietveld analysis, in TOPAS, for complex clay-bearing sample, which I'm having problems with. In the first model I tried to constrain lattice parameters of illite and biotite, to make TOPAS fit illite's and biotite's reflections to those observed in the qualitative analysis (I'm not sure of the correct position of these minerals' reflections, but both are supposed to be present in the sample). This gives 0% of biotite (it should be present in a small amount)and also cuts the basal peak of montmorillonite, so I removed biotite and changed the Chebychev background fucntion order from 4 to 5, which gave better results (model 2). Then (model 3) I've tried to put both illite and biotite without constraining their lowest/maximum values of lattice parameters and obtained anomalously low (?) amount of biotite. The remaining models are with Peaks Phase to describe the interlayer minerals. With Peaks Phase input the Rwp drops much, but also the amount of illite and kaolinite drops drastically. Also, their relative amounts change much. I'd like to ask, which model would you choose as correct one? I'm sure that there are no instrumental errors, as the geometry has been checked with LaB6 and Si standards. I would be grateful for any help...
Best regards! -- Łukasz Kruszewski, Ph.D., adjunct Polish Academy of Sciences Institute of Geological Sciences X-Ray Diffraction Laboratory (coordinator) Twarda 51/55 str. 00-818 Warsaw Poland -- Łukasz Kruszewski, Ph.D., adjunct Polish Academy of Sciences Institute of Geological Sciences X-Ray Diffraction Laboratory (coordinator) Twarda 51/55 str. 00-818 Warsaw Poland -- Łukasz Kruszewski, Ph.D., adjunct Polish Academy of Sciences Institute of Geological Sciences X-Ray Diffraction Laboratory (coordinator) Twarda 51/55 str. 00-818 Warsaw Poland
Rietveld_sample.doc
Description: MS-Word document
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Please do NOT attach files to the whole list <alan.he...@neutronoptics.com> Send commands to <lists...@ill.fr> eg: HELP as the subject with no body text The Rietveld_L list archive is on http://www.mail-archive.com/rietveld_l@ill.fr/ ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
