[Ifeffit] something is wrong with Ruthenium-Oxygen bond amplitudes

[Wayne W Lukens Jr]

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 <elena.montero at cimav.edu.mx>

> 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 <dr.scott.calvin at gmail.com>
>
> 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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>
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