[Ifeffit] huge S02 value ??

[Frenkel, Anatoly]

Hi Mengqiang,
 
I have done fits of aqueous solution of NiSO4 before and obtained S02 of 0.8 for the octahedrally coordinated Ni-O shell. You did not send the mu(E) data, just chi(k), so I was not able to compare my and your raw data fully, just in k-space. Here is what I found: my data is in perfect agreement in k-space with yours, only if I move E0 down to the pre-edge region, and I suspect, therefore, it is where you chose your E0.
 
As a result, the entire, very intense, main absorption peak became a part of your EXAFS, increasing the intensity of the k-space signal (since it became the first half-cycle of the EXAFS oscillation), and thus you got such a large S02. If you move your E0 to half-the edge jump, your result will be the same as mine, 0.8
 
Let me know if it helped,
Anatoly

________________________________

From: ifeffit-bounces at millenia.cars.aps.anl.gov on behalf of mzhu at udel.edu
Sent: Sat 4/4/2009 10:04 PM
To: ifeffit at millenia.cars.aps.anl.gov
Subject: [Ifeffit] huge S02 value ??



Hello everyone,
  I have been fitting EXAFS of NiSO4 aqueous solution. The feff files were created from Ni(OH)2 using Feff7.00. During the fitting, coordination number was fixed as 6. The S02 derived from fitting is 1.22. I tried other materials for creating feff files, such as NiCO3 and NiPO4, and I got the similar S02 values. I also tried Feff6, it did not result in a reasonable S02 value, either.
   Anyone can tell me why it led to such high S02 value? The data file and feff input file (Feff 7) are attached.  
   Thanks in advance.

Best wishes,

Mengqiang Zhu
 







-----------------------
Mengqiang Zhu
Ph.D Candidate
Environmental Soil Chemistry
Department of Plant and Soil Sciences
University of Delaware
152 Townsend Hall
Newark, DE 19716
http://ag.udel.edu/soilchem/zhu.html