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

Ni standard spectra
by Qiang 08 Jul '24

08 Jul '24

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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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Re: [Ifeffit] Creating a structure from EXAFS fitting
by Robert Gordon 27 Jun '24

27 Jun '24

Hi Lisa, Starting from a similar crystal structure could work. Alternatively, building a basic "crystal" structure using symmetry P1 and just putting the atoms where you want them would be feasible - tedious if you have a lot of atoms, easier if you know you have higher symmetry. e.g. Test Symmetry P1 * i.e. no symmetry a = 10 b = 10 c = 10 *Angstroms, easy to scale alpha = 90 beta = 90 gamma = 90 * so metrically cubic Central atom 0.000 0.000 0.000 * at origin, could always displace by 1/2 lattice constants to keep all in the unit cell 1st NNa 0.220 0.000 0.000 * 1st nns at 2.2 Angstroms away 1stNNb 0.000 0.220 0.000 1stNNc 0.000 0.000 0.220 1stNNd -0.220 0.000 0.000 etc... I've used this for modelling molecules, surfaces (with deposited films) as well as 3D crystals. It is a bit of brute force, but should work in any crystal visualization program... cheers, -R. On 2024-06-27 8:47 a.m., Lisa Langlois wrote: > Hello XAFS friends. I would like to know how to create a structure > model for a molecule that was measured with EXAFS, then modeled using > the typical strategies? - So, in the end you have some distances and > bond angles from the central atom > ZjQcmQRYFpfptBannerStart > This Message Is From an External Sender > This message came from outside your organization. > ZjQcmQRYFpfptBannerEnd > Hello XAFS friends. > I would like to know how to create a structure model for a molecule > that was measured with EXAFS, then modeled using the typical > strategies? - So, in the end you have some distances and bond angles > from the central atom to the first, and maybe second neighbor. > I was thinking that you start from a similar crystal structure and > then adapt that model using the numbers you got from EXAFS fitting, > using for example the Vesta program. > Best wishes, > Lisa. > > > > > Lisa Langlois, PhD > Beamline scientist > Rm 144 > Phone: +1 225-578-9341 > LSU-CAMD > 6980 Jefferson Hwy, Baton Rouge, LA 70806 > https://urldefense.us/v3/__https://www.lsu.edu/camd/__;!!G_uCfscf7eWS!adSZ4… > <https://urldefense.us/v3/__https://www.lsu.edu/camd/__;!!G_uCfscf7eWS!ZSSym…> > >

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Creating a structure from EXAFS fitting
by Lisa Langlois 27 Jun '24

27 Jun '24

Hello XAFS friends. I would like to know how to create a structure model for a molecule that was measured with EXAFS, then modeled using the typical strategies? - So, in the end you have some distances and bond angles from the central atom to the first, and maybe second neighbor. I was thinking that you start from a similar crystal structure and then adapt that model using the numbers you got from EXAFS fitting, using for example the Vesta program. Best wishes, Lisa. Lisa Langlois, PhD Beamline scientist Rm 144 Phone: +1 225-578-9341 LSU-CAMD 6980 Jefferson Hwy, Baton Rouge, LA 70806 https://urldefense.us/v3/__https://www.lsu.edu/camd/__;!!G_uCfscf7eWS!ZSSym…

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Al and Si references
by Amine EL MESSBAHI 10 Jun '24

10 Jun '24

Hi, Where can I find some Al and Si K-edge normalized data? Thank you, Amine El Messbahi email: amineelmessbahi(a)outlook.com

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alpha and σ2 values for EXAFS data fitting in Artemis came negative
by Arpita Nandy 04 Jun '24

04 Jun '24

Hello Everyone, During one of the data fittings in Artemis, alpha and σ2 came negative!!! What is/are the reason/s behind it? The corresponding file is attached... Regards, Arpita Nandy, PhD student Saha Institute of Nuclear Physics, India

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