Re: [Ifeffit] references

Hi Soma! Google "S02 transferability site:http://millenia.cars.aps.anl.gov/" and you'll find lots of messages on the subject if you haven't already. There's a post from Bruce on May 4 2010 where he writes: Recent work from John Rehr's group has elaborated on this, demonstrating that S02 is, in the strictest sense, neither transferable nor constant in energy. However, these effects are small such that chemical transferability remains a useful and defensible practice in many EXAFS analyses. http://millenia.cars.aps.anl.gov/pipermail/ifeffit/2010-May/009378.html I don't know what specific work he's referring to but that might be a good direction. -Jason On Tue, Jan 22, 2013 at 1:15 PM, Matt Newville wrote:

Hi Soma,

On Tue, Jan 22, 2013 at 11:11 AM, Soma Chattopadhyay wrote:

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2) A lot of times we find So2 from the respective metal foil and fix it when we fit the sample data for the same element. Is there any reference for this one?

I know about the book by Shelly, Hesterberg and Ravel. Would appreciate if I get some more references.

I'm not aware of a truly thorough study of this convention. Several of the early UWXAFS papers mention using this approach. Probably the clearest statement is from

E A Stern, et al "The UWXAFS Analysis Package - Philosophy and Details", Physica B208 pp 117-120 (1995) [DOI: 10.1016/0921-4526(94)00826-H]

which states (full paragraph):

The set of parameters that most frequently have a strong enough correlation to give difficulty in obtaining their values separately are S02, the passive electron overlap constant[13], sigma^2, the disorder about the optimal distance, and N, the number of atoms in a particular coordination shell. The most reliable way to separate out sigma^2 from the other two parameters is to measure the temperature dependence of sigma^2 and vary the product S02*N so as to obtain a fit to an Einstein oscillator, particularly the zero point value. Since S02 is dependent essentially on only the center atom, it can be found in known structures and N determined from the S02*N value.

Here Reference 13 is to Stern and Heald's chapter in the Handbook of Synchrotron Radiation Vol 1 (1983).

Cheers,

--Matt _______________________________________________ Ifeffit mailing list Ifeffit@millenia.cars.aps.anl.gov http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit