[Ifeffit] Large Enot values

[Paul Bingham]

Thanks Shelly.

I have tried doing as you suggest, shifting manually the value of E0 by +10 eV
in Athena before fitting in Artemis. Thankfully the delta E of the new fit is
close to zero which I think means that the theory and the data do agree, i.e. I
am fitting the first shell with the correct atom type. I am still a little
unclear as to why such a large energy shift might arise and will look into this
further. Any tips or suggestions would again be very welcome and I would very
much appreciate it if you can send me a copy of your book chapter which you
mentioned.

Best Regards

Paul.
-- 
Dr. Paul Bingham
Postdoctoral Research Associate
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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>    1. Re: Large Enot values (shelly Kelly)
> 
> 
> ----------------------------------------------------------------------
> 
> Message: 1
> Date: Fri, 11 Jun 2010 09:18:33 -0500
> From: "shelly Kelly" <dr.sdkelly at gmail.com>
> To: "XAFS Analysis using Ifeffit" <ifeffit at millenia.cars.aps.anl.gov>
> Subject: Re: [Ifeffit] Large Enot values
> Message-ID: <4c1245c4.9d90d80a.567d.3528 at mx.google.com>
> Content-Type: text/plain; charset="utf-8"
> 
> Hi  paul:
> 
> Have you tried to shift eo in athena by 10 ev? If you have and the fit still
> gives a large deltaE then the theory and the data do not agree.  DeltaE
> changes the spectra most strongly at low k, so another thing to try is to
> increase kmin in the ft. 
> 
> You can also use the theory to help remove the background in athena.  If
> you have tried all these and it doesn't work.  I'd try a different
> theory.  Either a different se oxide or a different atom type.
> 
> Of course my book chapter goes over how to do these thing. I'll send you a
> copy if you ask.  I've also posted example athena projects
> on xafs.org.
> 
> Good luck.
> 
> 
> 
> -- Sent from my Palm Pr?
> On Jun 8, 2010 5:55 PM, Paul Bingham <p.a.bingham at sheffield.ac.uk>
> wrote: 
> 
> Thanks Bruce,
> 
> 
> 
> I agree that the Se-O bond lengths are short but in SeO2, and Na2SeO3 as
> Se4+
> 
> "standards" there are Se-O bond lengths average around 1.7A. For example when
> I
> 
> run feff on the SeO2 cif file it gives 1 Se-O bond at 1.623A and 2 at
> 1.793A,
> 
> averaging at roughly 1.7A. 
> 
> 
> 
> I'm confident that the XANES I have for this sample show that the Se is
> pretty
> 
> much all present as Se4+ and I think the first shell is very likely to
> consist
> 
> of oxygens.
> 
> 
> 
> I also tried another shell from the same feff as included in the data I
> sent,
> 
> using O1_1 instead of O2_1 and the fit including Delr still points to an
> 
> average Se-O bond length of about 1.7A with an Enot of around 10.
> 
> 
> 
> I will try fitting with feffs based on different cif files with some
> different
> 
> Se-O bond lengths, but if you have any other suggestions I'd be grateful.
> 
> 
> 
> Thanks very much for your advice - it's appreciated.
> 
> 
> 
> Regards
> 
> 
> 
> Paul.
> 
> -- 
> 
> Dr. Paul Bingham
> 
> Postdoctoral Research Associate
> 
> 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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