[Ifeffit] EXAFS analysis of a sample having two metal centres with different coordination geometry

[Chris Patridge]

On 7/21/2011 3:44 PM, Abhijeet Gaur wrote:
> Hi all,
>           I am doing EXAFS analysis of a sample having two metal 
> centres with different coordination geometry. In my sample two  (Cu) 
> metal centres are present and these metal centres are surrounded by 
> different ligands (atoms) in different coordination geometry.
>           As I understand the EXAFS data of such sample will have 
> contributions from both the metal centres. So, in order to analyse the 
> EXAFS data, I have generated theoretical model (using Artemis) for 
> both the metal centres. Then, I have fitted these theoretical models 
> to the experimetal data.
>          But, I have some questions regarding this type of analysis as 
> I am not sure whether I going in right direction or not:
> 1. I have to fit these theoretical models one by one or simultaneously 
> to the experimetal data.
> 2. How can I confirm that whether the EXAFS data of the sample has 
> contributions from both the metal centres.
> 3. If one of the model does not fit well to the exp data, does this 
> mean that the corresponding metal centre is not present or the metal 
> centre is present but not contributing.
> 4. Is it possible to calculate the percentage of contributions from 
> different metal centres to the experimetal data.
>  If someone can suggest some available literature on this problem, it 
> will be really helpful to me.
> With thanks
> Abhijeet Gaur
> Research Scholar
> School of Studies in Physics
> Vikram University, Ujjain, India
>
>
> _______________________________________________
> Ifeffit mailing list
> Ifeffit at millenia.cars.aps.anl.gov
> http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit
Abhijeet,

This seems like a system which might require more information before 
using EXAFS analysis.  How did you come to the conclusion that there are 
two metal centers?  You begin by asking how to model two metal centers 
with different coordination and then in question 3, you lead the list to 
believe that there might not be two metal centers?  I assume you have 
found structural data for the sample?  You have different geometry as 
well as different ligands (atoms).  Do the metal centers only contain 
the absorbing metal or is it mixed?  If you had a bit more information 
about the material through other methods, I am sure several people could 
suggest helpful ideas for your analysis.

Chris

-- 
Christopher J. Patridge PhD.
405 NSC - Dept of Chemistry
University at Buffalo
State University of New York
Buffalo, NY 14260
Office:(716)645-4137
Contact:(315)529-0501
E-mail: patridge at buffalo.edu

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://millenia.cars.aps.anl.gov/pipermail/ifeffit/attachments/20110721/8272707f/attachment.html>