[Ifeffit] Problems with Reference Paths

[Matt Newville]

Hi Norbert,

On Fri, 11 Jul 2003, Norbert Weiher wrote:

> Cheers friends,
> 
> now a short question concerning reference paths calculated by FEFF (I use 
> FEFF8.1):
> 
> I have a series of spectra of catalysts containing V,P and O. Data was taken 
> at the V K edge. I know from literature, that the first coordination shell 
> should contain some 5-6 O atoms. The problem (and this is really the first 
> time I ever had problems with this) is that ifeffit (V 1.2.1) is not capable 
> of fitting even the first shell. As it works fine for model systems, e.g. Au 
> foil, I wonder if I have problems with the calculation of the references...
> 
> As first try, I re-calculated the feffxxxx.dat files with the SCF flag turned 
> on (which I never used before for the EXAFS) - the problem persisted. Has one 
> of you experienced similar problems and knows how to come over?

I'm not sure I understand the trouble you're having.  Could you send
an a more complete example?  You shouldn't need SCF for EXAFS.  In
fact, I'd recommend trying Feff7 or Feff6 if you're having trouble
with Feff8.1 calculations for EXAFS.

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--Matt