Re: [Ifeffit] [Ext] Re: Plotting chi(R) from FEFF in XAS Viewer (Larch) with phase correction

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 wrote:

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

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