[Ifeffit] Several Questions

Edward L. Kunkes kunkes at wisc.edu
Wed Apr 18 10:55:22 CDT 2007

Hello everyone,

 I am currently using IFEFFIT to fit LIII edge data collected for  Pt, Re 
 and PtRe bi-metallic Nan particles supported on carbon, and I have several questions:

1.	I get an So2 value of 0.54 from a first coordination shell fit on  
        Re-foil (this So2 value also seems to work when fitting NH4ReO4-) 
        Has anyone ever worked with Re before and gotten a similar value for So2 ?

2.	I model the path for the a single coordination shell as 6 octahedrally 
        arranged nearest neighbor atoms surrounding the absorber atom at a distance 
        equal to that of inter -atomic spacing in the metal. When comparing the IFEFFIT 
        predicted EXAFS for this model to one that is generated by using the first path from 
         a crystallographic model, the two seem slightly different.  The nanoparticles are 
        very small (amorphous to XRD), and probably consist of a disordered phase, so I cannot 
        assign a crystal structure. What should I do in this case?

3.	I often get high correlations  the coordination number and ss, or delEo and dR 
        (the correlations are ~0.8). Using multiple k-weights doesn’t decrease the correlations.
         What is an acceptable value for these correlations?  

Thank  you very much for taking the time to answer my questions

-Ed Kunkes

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