[Ifeffit] Small clusters in Feff

Kelly, Shelly D. SKelly at anl.gov
Thu Oct 6 10:21:29 CDT 2005


Hi EXAFS friends,

 

I was reading a paper this morning where the authors used a small
hydrated cluster in Feff8.2.  The cluster has a metal center surrounded
by one shell of oxygen atoms.

All feff paths in the calculation were used in the model fits.  No
mention was made in the manuscript of the muffin tin radii used in the
Feff8.2 calculation based on this small cluster, hence I assume that
these authors were unaware of the potential pit falls in doing so. 

 

Using feff7, I have run a comparison of the calculated signal from a
bounded and unbounded shell of atoms at the same distance.   I found
that the unbounded shell of atoms has a muffin tin radii that is really
big because it is not bounded by any other atoms giving rise to an error
in the calculated signal from these atoms.  Has anyone run this
experiment with Feff8.2?   

 

I have always used the metal-oxide crystal structure in my modeling of
hydrated metal ions and have found reasonable agreement with chemical
speciation calculations.  

I believe that the non-expert users of Feff, find it difficult to
remember not to use the exact model within Feff because of this
"feature".  Is there any discussion of adding a hydration sphere option
into Feff?  

 

I look forward to your comments.

Shelly

 

Shelly Kelly                   Bldg 203 RM E113

Skelly at anl.gov              Argonne National Laboratory

630-252-7376                 9700 S Cass Ave

www.mesg.anl.gov         Argonne, IL 60440

 

 

 

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