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@anl.gov Argonne National Laboratory 630-252-7376 9700 S Cass Ave www.mesg.anl.gov Argonne, IL 60440