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
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