[Ifeffit] Standard Mn(III) oxides for LCF fitting? problem in

[fred.mosselmans at diamond.ac.uk]

Dear Sathish,
You are right to be dubious about your Mn2O3 spectra, it looks to have much too small a white line compared to literature data and thus probably suffers from
Some sort of thickness effects. You can find some MnOxide spectra in Matt's data base
http://cars9.uchicago.edu/cgi-bin/newville/Model-Search.cgi

however the resolution may be different to wherever you collected your data, but the spectra should be better. Assuming all your data
was collected at the same time the edge position of your sample suggests by inspection that it is mainly Mn(IV),
In the recess of my mind i know people have published nicely correlated pictures of oxo-Mn compounds edge positions against oxidation states to get a nice linear plot. I am sure you can find this if you search for it in google scholar or the like.

However there are several different isomorphs of MnO2 and they have different XANES/EXAFS , thus LCF will only work if you have spectra of all of them (or at least all the types in your sample) Thus unless you are sure that delta is the only type in your sample (by XRD?) , LCF is not likely to get you very far. Given the edge position ab initio fitting might work OK.

Otherwise you need to track down absorption spectra of the other isomorphs and try again.
For LCF to work well (or at all) you need to have a basis set of all the components in your sample not just one for each possible oxidation state.

HTH
Regards
Fred




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