July 2024 - Ifeffit - millenia.cars.aps.anl.gov

Upcoming Q2XAFS, Data Formats, and request for data files
by Matthew Newville 07 Jul '24

07 Jul '24

Hi Folks, As some of you may have heard, there will be a virtual Q2XAFS (Quality and Quantity for X-ray Absorption Fine Structure) symposium series this summer, with presentations from Working Groups defined and formed at the 2023 Q2XAFS meeting in Melbourne last August. Details for this summer’s series are at https://urldefense.us/v3/__https://sites.google.com/view/q2xafs/home__;!!G_… , including a registration form. I will be giving the first of the presentations, on July 26 (0600 Seattle, 1400 London, 2200 Tokyo), describing the work of a Working Group on Data Formats and Metadata. Our Working Group has made good progress on defining a NeXuS/HDF5 definition for XAS data which is compatible with XDI and fits the typical NeXuS/HDF5 requirements. We have started working on tools to convert between XDI, NeXuS/HDF5, and even to help convert “raw” beamline data into this format, to make it easy to convert raw beamline data into these two formats for uploading to databases, data portals, supplemental information, etc. We have a pretty good collection of “real-world, as-collected” XAS data (see https://urldefense.us/v3/__https://github.com/XraySpectroscopy/pynxxas/tree… ) that we are working with as test cases. Please let us know if the data you get from your facility is in some other format (including binary files such as HDF5, or even into some database or “document store”). That is, if Larix or Athena struggles to read your data files, please let us know. If you can, please send an example file (you can send it directly to me or use https://urldefense.us/v3/__https://github.com/XraySpectroscopy/pynxxas__;!!… ). Thanks, --Matt

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Re: [Ifeffit] High-r range EXAFS fitting by Larch
by Robert Gordon 06 Jul '24

06 Jul '24

Hi Fan, I tried simulating BaSnO3 in Feff and played with the NLeg card to see the influence of multiple scattering: Blue curve is Nleg = 2 (backscattering only); red is Nleg=3 (backscatter + triangular multiple-scattering) Calcs done with DEBYE 100 307, CRITERIA 0 0, RPATH 9.5 Multiple-scattering (focused) seems to be strongly contributing both below 4Ang and below 8Ang. It seems possible that multiple scattering around the nearest neighbours may be more significant than the backscattering from 8.14Ang away. I haven't tried playing with decreasing the cluster size but keeping RPATH at 9.5Ang to see if NN MS is the culprit, but this may give you some ideas of what to check. cheers, -R. On 2024-07-05 1:45 a.m., FAN Dongxiao wrote: > Dear All, I met a problem about the misfit of EXAFS at high-range > (around 8 angstrom). My target is the B site EXAFS of perovskite > structure (BaSnO3, a=b=c=4. 105 angstrom) I want to study the > displacement correlation between the Sn and the > ZjQcmQRYFpfptBannerStart > This Message Is From an External Sender > This message came from outside your organization. > ZjQcmQRYFpfptBannerEnd > > Dear All, > > I met a problem about the misfit of EXAFS at high-range (around 8 > angstrom). > > My target is the B site EXAFS of perovskite structure (BaSnO3, > a=b=c=4.105 angstrom) > > I want to study the displacement correlation between the Sn and the > neighboring Sn atoms. > > For the first, second, and third Sn neighboring shells, the fitting is > good, but the Sn-Sn4 is bad in both amplitude and phase. > > I try to include the third cumulant, not become better. > > Can anybody tell me what’s the problem? > > I suspect the high frequency background signal of k space to produce > non-structure contribution in the FT spectra. > > But the data is very clean, I think this should not be the problem. > > Best, > > Fan >

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Re: [Ifeffit] High-r range EXAFS fitting by Larch
by Robert Gordon 06 Jul '24

06 Jul '24

Hi Fan, I tried simulating BaSnO3 in Feff and played with the NLeg card to see the influence of multiple scattering: Blue curve is Nleg = 2 (backscattering only); red is Nleg=3 (backscatter + triangular multiple-scattering) Calcs done with DEBYE 100 307, CRITERIA 0 0, RPATH 9.5 Multiple-scattering (focused) seems to be strongly contributing both below 4Ang and below 8Ang. It seems possible that multiple scattering around the nearest neighbours may be more significant than the backscattering from 8.14Ang away. I haven't tried playing with decreasing the cluster size but keeping RPATH at 9.5Ang to see if NN MS is the culprit, but this may give you some ideas of what to check. cheers, -R. On 2024-07-05 1:45 a.m., FAN Dongxiao wrote: > Dear All, I met a problem about the misfit of EXAFS at high-range > (around 8 angstrom). My target is the B site EXAFS of perovskite > structure (BaSnO3, a=b=c=4. 105 angstrom) I want to study the > displacement correlation between the Sn and the > ZjQcmQRYFpfptBannerStart > This Message Is From an External Sender > This message came from outside your organization. > ZjQcmQRYFpfptBannerEnd > > Dear All, > > I met a problem about the misfit of EXAFS at high-range (around 8 > angstrom). > > My target is the B site EXAFS of perovskite structure (BaSnO3, > a=b=c=4.105 angstrom) > > I want to study the displacement correlation between the Sn and the > neighboring Sn atoms. > > For the first, second, and third Sn neighboring shells, the fitting is > good, but the Sn-Sn4 is bad in both amplitude and phase. > > I try to include the third cumulant, not become better. > > Can anybody tell me what’s the problem? > > I suspect the high frequency background signal of k space to produce > non-structure contribution in the FT spectra. > > But the data is very clean, I think this should not be the problem. > > Best, > > Fan >

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Re: [Ifeffit] High-r range EXAFS fitting by Larch
by Robert Gordon 06 Jul '24

06 Jul '24

Hi Fan, I tried simulating BaSnO3 in Feff and played with the NLeg card to see the influence of multiple scattering: Blue curve is Nleg = 2 (backscattering only); red is Nleg=3 (backscatter + triangular multiple-scattering) Calcs done with DEBYE 100 307, CRITERIA 0 0, RPATH 9.5 Multiple-scattering (focused) seems to be strongly contributing both below 4Ang and below 8Ang. It seems possible that multiple scattering around the nearest neighbours may be more significant than the backscattering from 8.14Ang away. I haven't tried playing with decreasing the cluster size but keeping RPATH at 9.5Ang to see if NN MS is the culprit, but this may give you some ideas of what to check. cheers, -R. On 2024-07-05 1:45 a.m., FAN Dongxiao wrote: > Dear All, I met a problem about the misfit of EXAFS at high-range > (around 8 angstrom). My target is the B site EXAFS of perovskite > structure (BaSnO3, a=b=c=4. 105 angstrom) I want to study the > displacement correlation between the Sn and the > ZjQcmQRYFpfptBannerStart > This Message Is From an External Sender > This message came from outside your organization. > ZjQcmQRYFpfptBannerEnd > > Dear All, > > I met a problem about the misfit of EXAFS at high-range (around 8 > angstrom). > > My target is the B site EXAFS of perovskite structure (BaSnO3, > a=b=c=4.105 angstrom) > > I want to study the displacement correlation between the Sn and the > neighboring Sn atoms. > > For the first, second, and third Sn neighboring shells, the fitting is > good, but the Sn-Sn4 is bad in both amplitude and phase. > > I try to include the third cumulant, not become better. > > Can anybody tell me what’s the problem? > > I suspect the high frequency background signal of k space to produce > non-structure contribution in the FT spectra. > > But the data is very clean, I think this should not be the problem. > > Best, > > Fan >

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High-r range EXAFS fitting by Larch
by FAN Dongxiao 05 Jul '24

05 Jul '24

Dear All, I met a problem about the misfit of EXAFS at high-range (around 8 angstrom). My target is the B site EXAFS of perovskite structure (BaSnO3, a=b=c=4.105 angstrom) I want to study the displacement correlation between the Sn and the neighboring Sn atoms. For the first, second, and third Sn neighboring shells, the fitting is good, but the Sn-Sn4 is bad in both amplitude and phase. I try to include the third cumulant, not become better. Can anybody tell me what's the problem? I suspect the high frequency background signal of k space to produce non-structure contribution in the FT spectra. But the data is very clean, I think this should not be the problem. Best, Fan

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