Dear Guvenc,
Shelly and Scott have already replied to this issue, and I fully agree
with their points. Nevertheless, I'd like to add some points, that
generally apply to linear component fits.
The huge discrepancy between chi(k) and norm(E) fit very likely is an
indication that your data is not sufficiently described by your
standards. It might be that you're either using a standard component
that is not present in your system, or that you have not only two, but
three or more components in your system.
There is a number of ways to check which one could be the case. Very
often it helps to fit the system without the restriction that the
weights of the standards must sum to one. That way, you effectively
allow for the determination of a residual component during the fit. If
your system is sufficiently described by the standards, the weights of
the standards should sum to a constant value close to unity. The
difference to unity basically gives the residual.
If you have a non-negligible (or even concentration-dependent)
residual, PCA might help you to determine how many standard components
actually are required to fit the system. Be aware, though, that the
interpretation of PCA results is somewhat complicated. If PCA shows
that you need 4 linearly independent quantities to fully describe your
system, it doesn't necessarily mean that your system has 4 components.
Even temperature differences between scans might manifest as an
additional "component".
Cheers,
dominik
Quoting Guvenc Akgul
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?
regards
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-- Dr. Dominik Samuelis d.samuelis@fkf.mpg.de Max-Planck-Institut für Festkörperforschung Max Planck Institute for Solid State Research Heisenbergstr. 1 70569 Stuttgart Germany Phone +49-711-689-1769 Fax +49-711-689-1722 Web http://www.fkf.mpg.de/maier/