Hi Stanislav, Sorry I missed the point that the different E0's were for two different data sets!
a lower Rbkg/Rmin? No, I can not. 1.5A is around the minimum value in Chi(R) magnitude where the first peak can be separated from the others. However, the peak is a result of superposition of background, oxygen path and also
Can you get decent results with the alloy structure.
MN> I think I don't understand this. What are the "others" that the MN> first peak can't be separated from??
Sorry for the confusion that I have introduced. I am doing two-data set simultaneous fit (Bruce already mentioned that in the list) where the two absorbers are Ru and Pt atoms The model structure looks like this: 1. Ru data FEFF0(Ru-Ru):feff0001 FEFF1(Ru-Pt):feff0001 FEFF2(Ru-O):feff0001 2. Pt data FEFF3(Pt-Pt):feff0001 FEFF4(Pt-Ru):feff0001
I was talking about the first part of the model that is related to Ru data. What I meant was that around 1.0-1.5A I saw a peak. According to the model that peak was a result of overlap of background and contributions from different scatterers, such that I could not say that the peak was primarily because of oxygen or any other scatterer.
I think the above was what you described as:
'first shell peak', which is sometimes difficult to define for the asymmetric peak common with short metal-oxygen distances
Now if I set rmin=1.5A, the peak is not included in the R-range(it is below rmin). At lower values of rmin a part of the peak is in the range. That could be the reason why I was unable to get decent results with lower rmin.
Hmm, it does seems a little troubling, but it might be OK. I guess that's why you asked in the first place. Sorry I can't give a more definitive answer without looking at the data and/or fit. Does the Ru-Ru/Ru-Pt contribution overlap with Ru-O in this 'low-R peak'? Related to that: Is there a good understanding of why the Ru would partially oxidize while the Pt appears to not oxidize? This seems perfectly reasonable to me, but I'll ask anyway: you see Ru-O but not Pt-O right? If you see that the Pt edge background is OK and there's no need to add oxygen to the Pt model, that does make the need to include a 'background+oxygen peak' at the Ru edge more believable. But I'd still suggest looking at the different fit contributions in both k- and R-space. Hope that helps, even though you've probably tried all these things and more.... --Matt