February 2025 - Ifeffit - millenia.cars.aps.anl.gov

Water-free binder advice
by Paul Aronstein 01 Mar '25

01 Mar '25

Hello, I'm looking for some advice on binder alternatives for preparing either pellets or packed powder samples in a dry glovebox. Please also note if the binder requires preparation (i.e. desiccated prior to use, etc) or if there are other considerations. Thank you, -Paul

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Question about Ti edge
by Benito Melas 01 Mar '25

01 Mar '25

Hi all, I was following this article about Li2TiS3 https://urldefense.us/v3/__https://pubs.acs.org/doi/full/10.1021/acs.inorgc… and found this Ti edge XANES figure [image: image.png] The authors claim The peak position for LTS-213 is approximately 4970 eV, which agrees well > with that for rutile TiO2 with a valence of titanium species in the 4+ > oxidation state. Should we use the pre-edge to determine the oxidation state? Is it reliable, or should we use E₀ and compare it with references of well-known oxidation states? > In addition, TiS2, in which titanium is also in the 4+ oxidation state, > shows pre-edge peaks at 4968–4971 eV. (21) Considering the titanium > oxidation state in the raw materials, the stability of the titanium > species, and the XANES results, the oxidation state of the titanium species > in LTS-213 is likely to be 4+. The second conclusion is even more unclear. Would you help me see if I am missing something in my understanding of oxidation states using XANES? Best, B.

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Re: Question about Ti edge
by Benito Melas 28 Feb '25

28 Feb '25

Hi Matt, Thank you for the explanation. In this case, comparing oxides provides only a rough approximation of the oxidation states. Using both oxides and sulfides would incorporate the contribution of covalency and lead to inaccuracies. What about utilizing the pre-edge mixing oxides and sulfides? I have a concept that is more related to the symmetry of the site, although this understanding also originates from oxides. Best regards, On Fri, Feb 28, 2025 at 11:54 PM matt.newville(a)gmail.com < matt.newville(a)gmail.com> wrote: > Hi Benito, > > > > The energy of the sharp rise (ie, the energy of the empty metal 4p states) > is a simple measure of the “charge state” or “oxidation state” of a > metal. To be clear, for a particular ligand type (say, oxygen), the > energy of 4p states, and so also the energy of the main rise in mu(E), will > change systematically with energy. But if you change the ligand, and the > covalency/ionicity of the bond, that will also move the energy of the > metal’s 4p states. Metal sulfides are much more covalent than metal > sulfides, and many are semi-metallic. If I understand correctly, titanium > disulfide is used because it is electrically conductive. > > > > OTOH, titanium dioxide will have a band gap of a couple of eV. That “band > gap” is strongly correlated with the edge shift. > > > > Again, the energy of the “main edge” is just not a simple measure of > “oxidation state”, especially if the ligand is not oxygen. > > Using the term “oxidation state” for a sulfide is not going to give you > much insight. > > > > --Matt > > > > > > *From: *Benito Melas <metal.cnea(a)gmail.com> > *Date: *Friday, February 28, 2025 at 7:58 AM > *To: *matt.newville(a)gmail.com <matt.newville(a)gmail.com> > *Subject: *Re: [Ifeffit] Question about Ti edge > > Hi Matt, > As you mentioned, "for the transition metals, there will usually be a > sharp rise in mu(E) at the energy." > In the case of LTS, however, this sharp rise occurs at lower energies than > in TiO2, which raises concerns regarding the claim that both compounds > exhibit the same oxidation state. > Thank you for your continued dedication to enlightening our community. > Best regards, > > > > > > > > On Fri, Feb 28, 2025 at 3:46 AM matt.newville(a)gmail.com < > matt.newville(a)gmail.com> wrote: > > Hi Benito, > > > > > The authors claim > > >> The peak position for LTS-213 is approximately 4970 eV, which agrees > well with that for rutile TiO2 with a valence of titanium species in the 4+ > oxidation state. > > > > > Should we use the pre-edge to determine the oxidation state? Is it > reliable, or should we use E₀ and compare it with references of well-known > oxidation states? > > > > Many people use pre-edge peaks of transition metals for reliable analysis > of metal oxidation states. > > > > E0 is sort of poorly defined term. For the transition metals, there will > usually be a sharp rise in mu(E) at the energy of the metal’s own 4p > electrons – the “main edge”, though this can sometimes be tricky to > identify precisely, and sometimes has structure (as TiO2 does – slightly > different for its different forms). > > > > >> In addition, TiS2, in which titanium is also in the 4+ oxidation state, > shows pre-edge peaks at 4968–4971 eV. (21) Considering the titanium > oxidation state > > >> in the raw materials, the stability of the titanium species, and the > XANES results, the oxidation state of the titanium species in LTS-213 is > likely to be 4+. > > > The second conclusion is even more unclear. > > What confuses me there is “TiS2 is in the 4+ *oxidation* state”. > Titanium disulfide is not oxidized at all - it is bound to sulfur. Its > charge state could be 4+, and many chemists use “oxidation” to mean the > transfer of charge to and from a metal, whether this is done by oxygen or > not. For XANES, the ligand species matters. K-edge XANES shows the > energies of the unfilled p states at the center of the Ti atom, which will > be very different for Ti-S (more covalent) and Ti-O (more ionic) bonds. > > --Matt > > > > > > *From: *Benito Melas via Ifeffit <ifeffit(a)millenia.cars.aps.anl.gov> > *Date: *Thursday, February 27, 2025 at 7:28 AM > *To: *ifeffit(a)millenia.cars.aps.anl.gov <ifeffit(a)millenia.cars.aps.anl.gov > > > *Cc: *Benito Melas <metal.cnea(a)gmail.com> > *Subject: *[Ifeffit] Question about Ti edge > > Hi all, I was following this article about Li2TiS3 https: //pubs. acs. > org/doi/full/10. 1021/acs. inorgchem. 4c03864 and found this Ti edge > XANES figure The authors claim The peak position for LTS-213 is > approximately 4970 eV, which agrees well with > > ZjQcmQRYFpfptBannerStart > > *This Message Is From an External Sender * > > This message came from outside your organization. > > ZjQcmQRYFpfptBannerEnd > > Hi all, > > I was following this article about Li2TiS3 > > > https://urldefense.us/v3/__https://pubs.acs.org/doi/full/10.1021/acs.inorgc… > <https://urldefense.us/v3/__https:/pubs.acs.org/doi/full/10.1021/acs.inorgch…> > > > and found this Ti edge XANES figure > > > The authors claim > > > > The peak position for LTS-213 is approximately 4970 eV, which agrees well > with that for rutile TiO2 with a valence of titanium species in the 4+ > oxidation state. > > > > Should we use the pre-edge to determine the oxidation state? Is it > reliable, or should we use E₀ and compare it with references of well-known > oxidation states? > > > > In addition, TiS2, in which titanium is also in the 4+ oxidation state, > shows pre-edge peaks at 4968–4971 eV. (21) Considering the titanium > oxidation state in the raw materials, the stability of the titanium > species, and the XANES results, the oxidation state of the titanium species > in LTS-213 is likely to be 4+. > > > > The second conclusion is even more unclear. > > Would you help me see if I am missing something in my understanding of > oxidation states using XANES? > > > > Best, B. > > > >

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Diatomic distance on each EXAFS of both elements
by "Qiang Chang (常强)" 27 Feb '25

27 Feb '25

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Re: Water-free binder advice
by Michele Piana 27 Feb '25

27 Feb '25

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Not being able to generate FEFF paths from CIF
by cameron.mollazadeh＠colorado.edu 25 Feb '25

25 Feb '25

Hi! I have been trying to generate a FEFF path from a CIF I have however it hasn't worked. I tried pre-generating the inp file as well but it just stalls out and doesn't go anywhere. I have talked to some people In my lab who use the software as well and they also have encountered the same problems. It had worked once in the past for me but now is longer working. I have tried changing the unit cell and everything, however nothing is seeming to work. Best, Cameron

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Error saving Feffit results in Filtered X(k)
by DANILO OLIVEIRA DE SOUZA 21 Feb '25

21 Feb '25

Dear Matt, Firstly, I must congratulate you for your effort in making Larch such a nice, user-friendly, intuitive tool for XAS analysis. Cheers to you and all the collaborators. And thank you for making it available for the whole community. I would like just to report a (small) issue concerning saving Feffit results using Larix. After an EXAFS fitting, I tried successfully save the graphs in every option available, i.e., k-weighted chi(k), chi(R), Real[Chi(R)] and Filtered X(k). Everything works pretty well, except the last one, where an error can be observed on the prompt: File "C:\...\Python\Python311\site-packages\larch\wxxas\feffit_panel.py", line 2211, in onSaveFit ydata = getattr(ds0.data, yname)[:nx] * xarr**kw ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~ ValueError: operands could not be broadcast together with shapes (259,) (326,)" I do not know if it happens just on my version and I know it is a minor issue, since having the window used on back-FT we can plot it easily. In any case, I am just reporting the situation for your knowledge. Cheers, Danilo OLIVEIRA DE SOUZA

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Request for proposals to host International XAFS Conference 2028
by Bare, Simon R 15 Feb '25

15 Feb '25

International XAFS Conference 2028 Proposals to host the 2028 International XAFS Conference are now solicited and accepted. Proposal guidelines are given below, but if you have questions, please contact the IXAS Chair. Proposal Deadline: June 1, 2025 Proposal Presentations (videoconference): June 1 to July 1, 2025 Announcement of 2028 venue: During the 2025 XAFS Conference in Chicago https://urldefense.us/v3/__https://xrayabsorption.org/ixas-conference-selec… Send your proposal by email to the IXAS Chair: Asakura Kiyotaka kytkaskr(a)fc.ritsumei.ac.jp<mailto:kytkaskr@fc.ritsumei.ac.jp> Proposal Guidelines The proposal submitted for the conference can be made by email to the Chair by email and should include the following information. 1. Description of Proposed Conference Venue The conference proposal should include a description of the details about the venue for the conference (based on the 600 participants, the average number of recently held conferences), including: * One conference room for plenary sessions, accommodating 600 or more attendees. * Additional space for at least 200 posters, poster presenters, and sufficient room for attendees to view and discuss posters. * Additional conference rooms for parallel sessions which can accommodate at least 200 attendees each. Close proximity of rooms is to be secured for parallel sessions. * Projection and PA systems appropriate for a scientific conference in all conference session rooms. * One or more small meeting rooms for IXAS-EC, IUCr Commission on XAFS, and related executive meetings, which accommodates at least 30 attendees. * The main conference rooms are preferred to be climate-controlled. * Compliance with local regulations for disability access. 2. Description of Organization The conference proposal should name expected members of the conference organization including Chair(s). The conference organizers should form appropriate committees with different functions such as Local Committee, Program Committee, and International Advisory Committee, and the proposal should name some of the expected members of these committees. Please include: * CV and profile of the conference chair(s) * Letter(s) of commitment for host institution(s) and any other supporting institutions. * Proposed List of Local Committee members fully committed to the organization of the conference. * Proposed List of Program Committee members representing all relevant fields and topics. * Proposed list of Fundraising Committee. * Proposed List of an International Advisory Committee formed by the IXAS-EC members and other distinguished scientists selected by Conference Organizers taking into account regional and scientific balance. * Plan for circulating conference information to XAFS communities (Web site etc.). 3. Scope and Proposed Scientific Program The conference proposal should describe the scope of the scientific program for the conference, including * expected number of parallel sessions. * fields or special topics to be highlighted * plans for any satellite meetings (scope, locations, and expected number of attendants). * list of supporting organizations (institutes and academic societies). * expected plans for an exhibition. * expected tours of nearby scientific facilities. 4. Description of Infrastructure and Logistical Plan The conference proposal should provide a list of sufficient accommodations close to the conference venue, with a range of prices and an approximate number of rooms available. Transportation options between the conference venue and accommodation sites, restaurants, regional attraction sites, social events sites, etc. should also be given, as well as a description of transportation between airports or train stations and conference venue. 5. Preliminary Budget Draft Please include projections of the total cost, income breakdown, supports from institutes and other organizations, and start-up plan. Expected ranges for registration fees should be given. Also provide any expected details about support for young scientists, scientists from developing countries, and so forth. 6. Plans for Publication Conference Organizers should circulate the full conference program to all registered attendees prior to the conference. Conference Organizers are responsible for publishing Conference Proceedings with guidance and assistance from the IXAS. It is recommended that the proceedings are published in Radiation Physics and Chemistry as first choice or J Synchrotron Radiation as second choice. Simon R Bare Distinguished Scientist Stanford Synchrotron Radiation Lightsource SLAC National Accelerator Laboratory and Adjunct Professor Chemical Engineering University of California, Davis srbare(a)slac.stanford.edu<mailto:srbare@slac.stanford.edu> Ph: 650-926-2629 https://urldefense.us/v3/__https://web.slac.stanford.edu/coaccess/__;!!G_uC… [cid:image001.jpg@01DB7FBD.A7741230][cid:image002.png@01DB7FBD.A7741230]

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Artemis: Rejects first shell fitting
by avijay＠ethz.ch 14 Feb '25

14 Feb '25

Hello all, I am trying to fit my data using Artemis for a reference foil sample. However, the fit seems to get worse when I include the scattering paths at lowest R (i.e. the first shell scattering, with the highest rank). Does it make physical sense to not include this in the fitting? Is it acceptable to try and fit only a certain range of the |X(R)| vs R for the foil reference - in order to estimate the amplitude reduction factor for subsequent fitting of the real samples? Any insight/advice is much appreciated. Thank you. Best, A

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Constraining phase composition
by Olena Zavorotynska 09 Feb '25

09 Feb '25

Hello, I have been fitting in Artemis three phases to my samples, that I denote x, y, and 1-(x+y). It often happens that x and y get unreasonable or negative values. How do I constrain x, y to be positive, and x+y < 1? On a side note, I have simple metallic lattices, and fitting two samples at the same time so have enough independent points. Best regards Olena Zavorotynska Sent from my Galaxy

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