[Ifeffit] Problems with Reference Paths

Norbert Weiher norbertweiher at yahoo.de
Mon Jul 14 04:40:45 CDT 2003


Hi Matt,

okay - I attached a chi.dat file with the EXAFS to fit and a FEFF input file 
with which I did the reference paths. I tried to fit the first shell with the 
first five paths which came out of the FEFF calculation. The problem was that 
the algorithm really went somewhere - no matter what paths or path 
combinations I used in the fit.

The system is a VOHPO4 based catalyst and should have simply some 5-6 O atoms 
in the first shell. A comparison of the FT EXAFS with the literature looks 
reasonable.

Maybe it is a problem of the correct bg subtraction? I really don't know this 
time.

It might be a good idea to first do V2O5 or some similar compound. But 
unfortunately, I don't have spectra available. So if anyone has done V2O5 or 
something similar it would be great to hear of your experiences with this 
compound.

One last word to the catalyst sample: These V cats are lousy for EXAFS (lots 
of similar scatterers in slightly different positions). So it might be that 
an out of phase problem is the main point here.

Thanx for the help :)

Norbert

-- 
Dr. rer. nat. Norbert Weiher (norbertweiher at yahoo.de)
Laboratory for Technical Chemistry - ETH Hönggerberg
HCI E 117 - 8093 Zürich - Phone: +41 1 63 3 48 32
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#------------------------
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