[Ifeffit] Cu oxide fitting result

Bruce Ravel bravel at bnl.gov
Fri Oct 9 10:47:19 CDT 2009

On Thursday 08 October 2009 08:07:16 am abhijeet gaur wrote:
> Hi all,         I am fitting Cu2O data using Artemis. I got a very good
> fit. But there are problems with the parameters.
>     1)  The value of SO2 is coming very low
>     2)   The value of sigma*2 for different path is coming very different
> from each other.
>     3)   I have used  a number of paths for the fitting as one shell has
> contribution from many paths. Also the paths are very close to each other
> (i.e. Reff), So how I should report the fitting results.
>         I am not able to understand these results and also that where I had
> done mistakes, so please tell me.
>         The Artemis project file is attached herewith


I took a quick peak at your project and I find it very confusing.  In
the most recent fit, you are fitting only from 3.5 to 4.4 -- the area
under the *third* peak in the data.  I don't really know how to
comment on this project because you have set a large number of
parameters to seemingly arbitrary values.  From a numerical
perspective, the reason for questions 1 and 2 is because you are
attempting to fit only a narrow and of the data and you have set the
majority of your parameters.  That seems an unlikely strategy to me.

I think the best thing you could do would be to fit *all* of your data
rather than an arbitrary and small band of it.

It would probably be fruitful for you to study carefully Shelly's
example of analysis of SnO2 from her recent review chapter.  See



 Bruce Ravel  ------------------------------------ bravel at bnl.gov

 National Institute of Standards and Technology
 Synchrotron Methods Group at NSLS --- Beamlines U7A, X24A, X23A2
 Building 535A
 Upton NY, 11973

 My homepage:    http://xafs.org/BruceRavel
 EXAFS software: http://cars9.uchicago.edu/~ravel/software/exafs/

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