[Ifeffit] quotation of figures

[Bruce Ravel]

On Wednesday 16 July 2008 15:27:27 Scott Calvin wrote:
> Bruce--I'm not following your critique of the third panel. Where's the  
> confusion? I see the disorder term, and I see the mean-free path term,  
> but I don't see them inappropriately labeled or confused with each  
> other (aside from the common use of "Debye-Waller factor"). Unless  
> perhaps it's just that the spacing and arrows in the label "From ab-
> initio calculations or from reference compounds"  is confusing? (i.e.  
> it kind of looks at first like the slide claims that the mean-free  
> path comes from a reference compound)

Unless you redefine sigma^2 such that it has units of 1/angstrom^2 and
it subsumes the 2 we usually put in that exponential, the expression

    exp( -k^2 / sigma^2 )

is incorrect.  I concur that one is always free to define ones terms.
But redefining what sigma means in the exafs equation can only lead to
confusion.

(BTW, When you analyze your data by comparison to an empirical
standard, I would presume that the mean free path is considered to be
chemically transferable.)

B



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

 National Institute of Standards and Technology
 Synchrotron Methods Group at NSLS --- Beamlines U7A, X24A, X23A2
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 My homepage:    http://xafs.org/BruceRavel
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