Plotting chi(R) from FEFF in XAS Viewer (Larch) with phase correction
Dear all, In Artemis it is possible to plot chi(R) for FEFF-fit, with the phase corrected - i.e. bond length corrected for deltaR. This is shown in this screenshot below ("Use this path for phase corrected plotting"). Is this possible in XAS Viewer? [cid:b58a0f44-1946-4c60-a12e-c1e0bfa50100] Liam Nagle-Cocco (he/his) PhD Student in Condensed Matter Physics | Cavendish Laboratory Welfare Officer 2022-2023 | Jesus College MCR
Hi Liam,
Yes, this is not currently available. It would not be hard to enable, but
I am not sure it is a great thing to do. I admit that I sort of find that
phase-correction plots need a lot of explanation, and so are prone to
causing confusion. They might be useful for Pt metal, but they cannot
really be correct for multi-atomic systems. Well, I guess "correct" is not
the only consideration ;).
I guess I would ask if there are suggestions and input from people teaching
XAFS on whether phase corrections (and probably a handful of other "tricks"
or analysis variations) are actually useful or just confusing.
On Tue, Dec 13, 2022 at 7:58 AM Liam Nagle-Cocco
Dear all,
In Artemis it is possible to plot chi(R) for FEFF-fit, with the phase corrected - i.e. bond length corrected for deltaR. This is shown in this screenshot below ("Use this path for phase corrected plotting"). Is this possible in XAS Viewer?
Liam Nagle-Cocco *(he/his)*
PhD Student in Condensed Matter Physics | Cavendish Laboratory
Welfare Officer 2022-2023 | Jesus College MCR _______________________________________________ Ifeffit mailing list Ifeffit@millenia.cars.aps.anl.gov http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit Unsubscribe: http://millenia.cars.aps.anl.gov/mailman/options/ifeffit
-- --Matt Newville <newville at cars.uchicago.edu> 630-327-7411
Hi Liam:
I agree with Matt. I don't find phase corrected plots to be very useful.
Rather, I try to just identify peak positions without trying to interpret
what the half-path length might be. I leave that for the results of the
fitting. As a secondary, but perhaps more important point, applying the
phase correction in a plot of the Fourier Transform is only an approximate
calculation because the correct phase shift depends on the identity of the
scattering atom and you don't really know that until you have a path model
in the fitting routines. Once the fitting is done, then you could in
principle phase correct both the data and fit but why bother?
Carlo
On Tue, Dec 13, 2022 at 4:53 PM Matt Newville
Hi Liam,
Yes, this is not currently available. It would not be hard to enable, but I am not sure it is a great thing to do. I admit that I sort of find that phase-correction plots need a lot of explanation, and so are prone to causing confusion. They might be useful for Pt metal, but they cannot really be correct for multi-atomic systems. Well, I guess "correct" is not the only consideration ;).
I guess I would ask if there are suggestions and input from people teaching XAFS on whether phase corrections (and probably a handful of other "tricks" or analysis variations) are actually useful or just confusing.
On Tue, Dec 13, 2022 at 7:58 AM Liam Nagle-Cocco
wrote: Dear all,
In Artemis it is possible to plot chi(R) for FEFF-fit, with the phase corrected - i.e. bond length corrected for deltaR. This is shown in this screenshot below ("Use this path for phase corrected plotting"). Is this possible in XAS Viewer?
Liam Nagle-Cocco *(he/his)*
PhD Student in Condensed Matter Physics | Cavendish Laboratory
Welfare Officer 2022-2023 | Jesus College MCR _______________________________________________ Ifeffit mailing list Ifeffit@millenia.cars.aps.anl.gov http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit Unsubscribe: http://millenia.cars.aps.anl.gov/mailman/options/ifeffit
-- --Matt Newville <newville at cars.uchicago.edu> 630-327-7411 _______________________________________________ Ifeffit mailing list Ifeffit@millenia.cars.aps.anl.gov http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit Unsubscribe: http://millenia.cars.aps.anl.gov/mailman/options/ifeffit
-- Carlo U. Segre (he/him) -- 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 http://phys.iit.edu/~segre segre@debian.org
participants (3)
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Carlo Segre
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Liam Nagle-Cocco
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Matt Newville