[Ifeffit] Linear combination fitting
Scott Calvin
SCalvin at slc.edu
Tue Apr 7 09:44:27 CDT 2009
Hi Guven,
This is not unusual, in my experience, particularly if the chi(k) fit
is not particularly good.
XANES and EXAFS are sensitive to different aspects of the local
environment. In particular, the chi(k) is much more affected by
structure beyond the nearest-neighbors. In your system, it is unlikely
that you "really" have a mixture of bulk ZnO and bulk ZnTiO3. For
nearest neighbors, those two standards may be good enough, and may
give you a decent fit to XANES that has some physical meaning. But for
chi(k) those standards may not be sufficient, and, while the fit is
doing what it can, the fractions may not be particularly physically
meaningful. One piece of evidence that this is going on is if the
chi(k) fit is "poor," that is, if the fitted chi(k) does not
correspond well to the data.
--Scott Calvin
Sarah Lawrence College
On Apr 6, 2009, at 5:31 PM, Guvenc Akgul wrote:
> Dear all,
>
> I have done Ti doped ZnO EXAFS data analysis but I guess it is
> getting mixture structure at high concentration for example 55% Ti
> doped ZnO.Also I done linear combination fit , but at fitting space
> norm(E),ZnO weight is 0.779 and ZnTiO3 is 0.221 then I changed
> fitting space is chi(k) ZnO weight is getting 25.2 and ZnTiO3 is
> getting 74.8 and it is not same like at fitting space norm(E) why?
>
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