Let me break the tie: here is what I just received from one of the people cc'd to in Steven's email. This problem is indeed even more complex than we all think.
 

Dear Anatoly,

The problem is even more complex:
- there is one Co2+ species in tetrahedral environment;
- there are small (20 - 100 atoms) metallic clusters;
- there is an intermediate Co+1 like species in tetrahedral coordination.
All these species may be present in some of the samples. Plus, I assume the
Co-O distance between Co in small metallic clusters and oxygen in the
silica is different than that between Co2+ ions and O2- ions in the cobalt
oxide - like compound, which adds to the complexety.
We feel like we're chasing our tail with this thing...:)

Dragos


-----Original Message-----
From: ifeffit-bounces@millenia.cars.aps.anl.gov [mailto:ifeffit-bounces@millenia.cars.aps.anl.gov]On Behalf Of Scott Calvin
Sent: Friday, May 06, 2005 5:09 PM
To: XAFS Analysis using Ifeffit
Subject: Re: [Ifeffit] Need an advice

Hi Matt, The quote below is where I got the idea that Steven was interested in size-determination of nanoparticles, but I may have misunderstood...maybe he meant to use the fraction of oxide as a marker for the surface to volume ratio? In any case, that still makes me think that he expects to have nanoscale particles... --Scott Calvin Sarah Lawrence College At 03:12 PM 5/5/2005 -0400, Steven wrote: >>>> However, if what we have is closer to a physical mixture of small Co metal particles and Co oxide particles, it would seem that it would be more appropriate to analyze separately the windowed Co-O and Co-Co peaks in R-space, to somehow normalize the Co-Co to the fraction of metal in the sample and use this as a qualitative measure of metal particle size.