Re: [Ifeffit] [Ext] Analyzing EXAFS data on Artemis

If you go beyond first shell, then you'll need to take into account the Se-Se paths in Li2Se. That may be your best way of detecting Li2Se. mam On 5/27/2021 12:03 PM, Carlo Segre wrote:

Hi Deltsidis:

Using Artemis, you can compare the calculated Fourier Transforms of the Se-Fe and Se-Li paths to see if the latter will actually be visible.  I suspect that it will not if it is an impurity phase with small phase fraction.  I would probably start with only Se-Fe and see how well it can fit the data.

The eins(T, thetae) is the temperature dependent term.  What is missing the static disorder that needs to be added into the sigma^2 to account for the temperature independent residual disorder.

Carlo

On Thu, May 27, 2021 at 9:43 AM Alexandros Deltsidis mailto:adeltsidis@iesl.forth.gr> wrote:

Dear mailing list,

I am currently analyzing some EXAFS data. I am studying a Lix(C5H5N)FeSe system in a temperature grid that extends from 20 K to 300 K and I have 4 such datasets which correspond to different amount of doping (x). Right now, im focusing on fitting the 1st coordination cell, in Artemis for the Se K-edge. My starting model is the simple P4/nmm FeSe. So, in my system the 1st coordination cell, in the Se K-edge, corresponds to the Se (absorber) - Fe (backscatterer) pair. I have 2 questions: 1) I realize now, that I have a certain impurity in the high doping range on my system, namely Li2Se. I try to include a scattering path from the respective Li2Se crystal model in my fits, since a Se (absorber) - Li (backscatterer) pair is present in the R-range of my fit in the Forward Fourier Transform. My question here is if this makes sense since Li is much smaller scatterer compared to Se. In other words, does it make sense to look for physical parameters (Li-Se bond length and DW factor respectively) of a signal (Se-Li) that is "tucked" in below the main peak coming from the "majority" Se-Fe signal in the FFT? 2)Also, I'm attempting to extract an Einstein temperature for each of those datasets, by utilizing the "eins(T, thetae)" function implemented in Artemis. What is the equation that is parametrized here? Does it include the s0^2 offset term that accounts for the overall configuration disorder in the system? And if that is the case is there same way to separate it from the temperature dependent s^2 term?

Thank you in advance, Deltsidis Alexandros PS:I am attaching a png. file exported from Artemis that is relative to my question 1)

Ph.D candidate, Institute of Electronic Structure and Laser (IESL), Foundation for Research and Technology - Hellas (FORTH)_______________________________________________ Ifeffit mailing list Ifeffit@millenia.cars.aps.anl.gov mailto:Ifeffit@millenia.cars.aps.anl.gov http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit Unsubscribe: http://millenia.cars.aps.anl.gov/mailman/options/ifeffit http://millenia.cars.aps.anl.gov/mailman/options/ifeffit

-- Carlo U. Segre -- Duchossois Leadership Professor of Physics Professor of Materials Science & Engineering Director, Center for Synchrotron Radiation Research and Instrumentation Illinois Institute of Technology Voice: 312.567.3498            Fax: 312.567.3494 segre@iit.edu mailto:segre@iit.edu http://phys.iit.edu/~segre http://phys.iit.edu/~segre segre@debian.org mailto:segre@debian.org

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