[Ifeffit] help: can I use ifeffit to predict chi?
tychen at mail.chem.tamu.edu
Fri Nov 2 12:53:38 CDT 2007
Thanks for the valuable information. I have tried the
sum of pathes method to do the estimation.
But it seems like not to accurtate compared to the data I
found in the paper.
So, I want to go back to the the proper fit fo find out
poper sigma^2 and eo.
But I don't have any numeric chi data for gamma-Fe2O3. Do
you have any idea where I may get these
information? Thanks for all the help.
On Thu, 1 Nov 2007 10:38:35 -0400
Bruce Ravel <bravel at bnl.gov> wrote:
> On Tuesday 30 October 2007 21:21:59 Tai-Yen Chen wrote:
>> Can anyone tell me whether I can use ifeffit to do
>> I want to know the % change in chi when the molecule
>> 3% change in radius?
>> All I have is just the crystal struture of gamma-Fe2O3,
>> which means I can only get the Feff.
>> How can I introduce 3% change in redius so that I can
>> the difference of chi?
>> Can anyone help me? Tanks a lot.
> Hi TaiYen,
> Since you are asking about using Ifeffit, I presume that
> interested in changes in the EXAFS spectrum rather than
> There are a number of ways you might approach this
> the best way of doing so would be to do a proper fit to
> so that you can get a good measure of things like
>sigma^2 and e0.
> Then, using the results of the fit, modify the deltaR
> each path used in the fit to be 3% larger. Then simply
>add up the
> paths using the fitted values for sigma^2, e0, and so
> You can also do something similar without actually doing
>a fit to
> data. Use Artemis or ifeffit itself to increase R for
>each path and
> simply sum the paths without using fitted values for
>sigma^2 and so
> on. The easiest way of doing so would be to set deltaR
>for each path
> equal to "0.03*reff". That will expand the length of
>each path by 3%,
> thanks to the magic of the special "reff" parameter in
> Another way of doing this (and a decent way of doing so
>for a XANES
> calculation) would be to use Feff's rmultiplier keyword:
> Bruce Ravel -----------------------------------
>bravel at bnl.gov
> National Institute of Standards and Technology
> Building 535A, Room M7
> c/o Brookhaven National Laboratory
> Upton NY, 11973, USA
> My homepage: http://xafs.org/BruceRavel
> EXAFS software:
> Ifeffit mailing list
> Ifeffit at millenia.cars.aps.anl.gov
TaiYen Chen 979-739-7772
Department of Chemistry
Texas A&M University
P.O. Box 30012
College Station, TX 77842-3012
Visit us on the web at http://www.chem.tamu.edu
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