Hi Maria Elena,
Your RuO2 spectrum does not look right to me. Here is a spectrum that I
obtained on 11-2
in transmission. The sample is RuO2 powder brushed onto tape (16 layers of
tape). Feff 7
fits the data well (amp is 1.1 for the oxygen shell if I allow it to vary).
I think you my have either a sample or data collection issue. Since you
have a good XRD, I would suspect the latter.
For what it's worth, I have had problems with Ru metal and Feff and had to
reduce amp to around 0.7 (if I remember correctly) to get a good fit.
Sincerely,
Wayne
2010/11/5 María Elena Montero Cabrera
Hi Scott! Thanks a lot for your interest. The physical form was powder, and they were measured by transmission and fluorescence. We have tried firstly the fitting of fluorescence spectra, but we have obtained that low amplitude values. So I have though we have autoabsorption, and decided to do the fitting of transmission spectra. They are not exactly the same, close to the edge fluorescence spectra have lower mu(E). I remember that Sam Webb told me that the K edge jump was good in the absorption spectra, after calculating the thickness with Hephaestus. In that fitting we have obtained the same "wrong" values. Then we decided to do the fitting of RuO2, and we have obtained again the low amplitudes. Now I don't know what to do. Regards Maria Elena
2010/11/5 Scott Calvin
Hi Maria,
What was the physical form of the samples (powder, thin film, etc.) and how were they measured (transmission, fluorescence, ...)? Sometimes this kind of thing can stem from sample/beamline/data effects.
--Scott Calvin Sarah Lawrence College
On Nov 5, 2010, at 5:50 PM, María Elena Montero Cabrera wrote:
Hello friends,
Hopping someone could help us. We are having some problems in fitting Ru K-edge in a Ruthenium-cuprate sample on Artemis, with path functions obtained using FEFF 8.4, where we got amplitude values of less than 0.50 for Ru-O first shells. We think this value probably is wrong, although there are some publications where some oxygen deficiency is studied and recorded as true. The ATOMS input data was found to be ok due to the Rietveld analysis results told us these are good. The reason we think we may be wrong with something during the fitting appeared because we tried to fit our reference sample of RuO2 (measured under same conditions as the experiment of Ru-Cu at SSRL) and we came to the same results, even worst, of amplitude lower than 0.40. We are attaching the Artemis files so you can take a look on it and give us some light to continue with our analysis. Thanking in advance, take care
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-- María Elena
Dra. María Elena Montero Cabrera Centro de Investigación en Materiales Avanzados (CIMAV) Miguel de Cervantes 120, Compl. Ind. Chihuahua Chihuahua CP 31109, Chih. México Tel (614) 4391123
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