[Ifeffit] Need an advice

Anatoly Frenkel frenkel at bnl.gov
Fri May 6 16:12:14 CDT 2005

Re: [Ifeffit] Need an adviceLet 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...:)


  -----Original Message-----
  From: ifeffit-bounces at millenia.cars.aps.anl.gov
[mailto:ifeffit-bounces at 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.
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