Re: [Ifeffit] Exploring XANES data for getting EXAFS results

There is also Smolentsev and Soldatov's work using FitIT as well as FDMNES and FEFF G. Smolentsev and A.V. Soldatov "FitIt: new software to extract structural information on the basis of XANES fitting http://dx.doi.org/10.1016/j.commatsci.2006.08.007" Comp. Matter. Science 39 (2007) 569. http://journals.aps.org/prb/abstract/10.1103/PhysRevB.75.144106 http://www.nano.sfedu.ru/fitit.html Though I haven't tried it myself, Grigory did give an interesting talk on to the APS XAFS community some years ago. On 1/16/2015 9:53 AM, Matt Newville wrote:

On Fri, Jan 16, 2015 at 9:21 AM, Marcelo Alves mailto:mealves@gmail.com> wrote:

Hi all,

I wonder if it is possible from XANES unusual data treatment to get information such as number and distances of neigbhors in the first and second shells.

There is an old-ish (like, from the 1950's I think) and fairly heuristic rule that the XANES edge energy shifts scale as 1/R^2 for the nearest neighbor. I think that Grant Bunker has a nice set of slides showing this, somewhere on the web. For example, I think this explains well slight energy shifts in the peak energy of the sulfate resonance. My recollection is that it works pretty well for many well-constrained set of spectra, but isn't quite as quantitative and readily applicable to unknown systems as one might hope.

It's also sort of related to the idea of bond-valence that, for a given class of systems (say, oxides of a particular metal), R, N, and formal valence state are not independent quantities.

--Matt

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