[Ifeffit] EXAFS analysis of homonuclear metal clusters

Bruce Ravel ravel at phys.washington.edu
Fri Jul 30 14:24:41 CDT 2004


On Thursday 29 July 2004 08:49 pm, m.bondin at pgrad.unimelb.edu.au wrote:
> Is there any way of determining if this small difference in energy, and
> hence E0, between the Fe atoms in the clusters can or cannot be neglected
> in modelling the EXAFS?

The generic answer to this sort of question is that the fit should
tell you what the data will support.  Are the data well fit in the
R-factor sense?  Are the fitted values for e0 different outside their
error bars?  Does the reduced chi-square value decrease significantly
when you add the many e0 values?  Are the e0 values physcially
justifiable?  Are the other parameters physically reasonable?

At the end of the day you may be inclined to believe a particular
fitting model, but not solidly convinced.  That is not a failure of
analysis (either by the software or by its user), it just means that
the data is supported by a particular model, but not conclusively.  In
that case, I would say it is good science to report your inclination
so long as you also report an honest assessment of the data and an
honest assessment of your uncertainty in the result.

HTH
B

-- 
 Bruce Ravel  ----------------------------------- ravel at phys.washington.edu
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 Naval Research Laboratory                          phone: (1) 202 767 2268
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 NRL Synchrotron Radiation Consortium (NRL-SRC)
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 National Synchrotron Light Source
 Brookhaven National Laboratory, Upton, NY 11973

 My homepage:    http://feff.phys.washington.edu/~ravel 
 EXAFS software: http://feff.phys.washington.edu/~ravel/software/exafs/




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