[Ifeffit] Large Enot values

[Paul Bingham]

Hi,

I have been struggling with a tricky problem and cannot resolve it - hopefully
someone out there can help!

I have collected fluorescence XANES and EXAFS at the Se K-edge and I'm
currently
trying to fit the EXAFS (see attached files). The XANES agrees very well with a
number of my standards and shows that the vast majority, if not all, of the Se
is present in this material (an amorphous oxide-based system) as Se4+.

I have tried to fit the EXAFS using a single Se-O path from a range of cif
files
(the simplest being SeO2). Other ions than O present incorrect bond lengths and
I am convinced the first shell is oxygen. I can obtain a decent fit in terms of
most parameters, as long as I disregard the consistently high value of Enot.
Guidelines indicate that Enot should be less than about 5(ish), but I
consistently get values of 10-12 when I try to fit my spectra, of which one is
present in the attached files. 

I have checked my background subtraction and tried as many different options,
changes and tweaks that I know or can find suggested (too many to list here)
but I cannot obtain a fit with Enot below about 10 and so I ask my colleagues
out there who are more experienced than I with EXAFS - can anyone shed any
light on (a) the potential cause/s and (b) any potential solution/s?

Thanks in advance for your time.

Best Regards

Paul Bingham
-- 
Dr. Paul Bingham
Immobilisation Science Laboratory
Dept. of Engineering Materials
University of Sheffield
Mappin Street
Sheffield
S1 3JD
UK

Email: p.a.bingham at sheffield.ac.uk
Direct Line: (0114) 2225473



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