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

E0 in Co3O4
by Jesús Eduardo Vega Castillo 30 Oct '17

30 Oct '17

Dear list, I enclose an Athena project with a XAFS spectrum of Co3O4 with a metallic Co reference. Athena by default has chosen E0 at the absolute maximun of the derivative curve (at 7727.8eV) which in my opinion is too high because it is at the white line zone. I believe that E0 should be the previous maximun in the derivative at around 7722eV, which would be at the rising edge. Am I wrong? I would appreciate some help with the criterion to determine the right value. Yours, Jesús

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Re: [Ifeffit] iron carbide fitting with Artemis
by fred.mosselmans＠diamond.ac.uk 28 Oct '17

28 Oct '17

Dear Yunyun, I don't think Mike has written anything particularly incorrect , but he didn't point out why this approach is necessary. I believe there are two things you should definitely be aware of. An EXAFS dataset has a very limited amount of information. Approximately deltak.deltaR no of variables can be fitted To any spectrum as an absolute maximum and preferably quite a lot fewer than this (where deltak and deltaR are your fitted data range in k and R space respectively. Because of this if say you know you have N C atoms at ca G angstroms around your central atom. It is best not to use a variable for fit the degeneracy for that path but set it at the number you know is correct. And secondly because an EXAFS spectrum is effectively a collection of Sine waves there is a limited resolution, i.e. you cannot resolve paths of the same atom type that are less then Pi/2k(max) A apart, where k(max) is the maximum range of your dataset in k space, and Pi is Pi. Hence to separate two paths of the same atom that are 0.1 A apart you need about 15k worth of data. Regards Fred -- This e-mail and any attachments may contain confidential, copyright and or privileged material, and are for the use of the intended addressee only. If you are not the intended addressee or an authorised recipient of the addressee please notify us of receipt by returning the e-mail and do not use, copy, retain, distribute or disclose the information in or attached to the e-mail. Any opinions expressed within this e-mail are those of the individual and not necessarily of Diamond Light Source Ltd. Diamond Light Source Ltd. cannot guarantee that this e-mail or any attachments are free from viruses and we cannot accept liability for any damage which you may sustain as a result of software viruses which may be transmitted in or with the message. Diamond Light Source Limited (company no. 4375679). Registered in England and Wales with its registered office at Diamond House, Harwell Science and Innovation Campus, Didcot, Oxfordshire, OX11 0DE, United Kingdom

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iron carbide fitting with Artemis
by Yunyun Zhou 28 Oct '17

28 Oct '17

Hello All, I am having trouble fitting my sample with both Fe5C2 and Fe3O4 as standards. Hopefully somebody could help me out and I really appreciate it. My iron sample was mainly iron carbide in the core and iron oxide on the shell. Fe5C2 has a monoclinic structure and generated complicated FEFF paths. Many of the paths have similar distances. I have found some paper reported their results as follows, which apparently combined several paths together and assume they have similar path length. My first question is does someone know how they did it? It seems that combing similar paths makes fitting much easier, but I am not sure whether this is a correct way to do the fitting. My second question is regarding fitting with the two combined models of Fe5C2 and Fe3O4. I haven't fit with two models before. Is it just like what I did in the attached Artemis file? Shall there be any restrictions between the two models and do I have to fix some of the parameters? Thank you very much in advance for your help! Best, Yunyun Zhou Fe5C2 FEff paths: [image: Inline image 1] Literature reported results: [image: Inline image 2]

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monoclinic elemental selenium data
by George Sterbinsky 26 Oct '17

26 Oct '17

Hello, I am trying to help someone locate XAFS data collected from the red allotrope (monoclinic) of elemental selenium. Does anyone have a data set they are willing to share? Thank you, George

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flattened norm export issues
by Robert Gordon 22 Oct '17

22 Oct '17

Hi, Encountered a difference on export of normalised data. Flattening does not seem to be preserved when saving current group as norm(E) but is when saving marked group. Example in norm.prj attached. original data set normalised and flattened...displaying "Normalized" as current group or as marked group looks the same: current: marked: On saving current or marked group as norm(E), re-importing and plotting as mu(E) marked is still flattened, but the set exported using "save current group as" is not flattened. Similar difference saving "marked" versus saving "each marked" So it seems only "Save marked group as..." preserves flattening for norm(E). -R.

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space group 224 & Atoms
by Robert Gordon 22 Oct '17

22 Oct '17

Hi, I was trying to simulate Cu2O...cubic...O tetrahedrally coordinated by Cu...Cu linearly coordinated by O. There are two origin choices for space group 224 (Pn-3m). If using origin choice 1, then atom positions would be O 0,0,0 Cu 0.25,0.25,0.25 If using origin choice 2, translate by -0.25,-0.25,-0.25 to get O 0.75,0.75,0.75 Cu 0,0,0 (or use the shift vector in Atoms...) My understanding is that Demeter defaults to the 2nd origin choice. Problem I am having is that neither gives me linearly coordinated copper using current Atoms. If I read in the attached atoms.inp (choice 2) and Run Atoms, the ATOMS list in the Feff output begins with: ATOMS * this list contains 87 atoms * x y z ipot tag distance 0.00000 0.00000 0.00000 0 cu1 0.00000 -1.06675 1.06675 1.06675 2 o1.1 1.84767 -1.06675 -1.06675 1.06675 2 o1.1 1.84767 1.06675 1.06675 -1.06675 2 o1.1 1.84767 -1.06675 -1.06675 -1.06675 2 o1.1 1.84767 2.13350 2.13350 0.00000 1 cu1.1 3.01722 I get 4-coordinate instead of 2-coordinate. If I try origin choice 1, almost the same result.... ATOMS * this list contains 83 atoms * x y z ipot tag distance 0.00000 0.00000 0.00000 0 cu1 0.00000 -1.06675 1.06675 1.06675 2 o1.1 1.84767 1.06675 -1.06675 1.06675 2 o1.1 1.84767 1.06675 1.06675 -1.06675 2 o1.1 1.84767 -1.06675 -1.06675 -1.06675 2 o1.1 1.84767 2.13350 2.13350 0.00000 1 cu1.1 3.01722 If I run choice 1 with the shift vector, I do reproduce the choice 2 result. If I use the old dos version of Atoms with origin choice 2, I do get linearly coordinated copper: ATOMS .00000 .00000 .00000 0 cu1 .00000 -1.06675 -1.06675 -1.06675 1 o1 1.84767 1.06675 1.06675 1.06675 1 o1 1.84767 .00000 -2.13350 2.13350 2 cu1 3.01722 SPECS: Demeter 0.9.26 (pre2) Win10x64 AMD64 -R.

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Metal-Metal Peak Splitting in 5d Transition Metals
by Shoaib Muhammad 19 Sep '17

19 Sep '17

Dear All, I have a question that is not directly related to Athena or Artemis but it is more related with EXAFS theory. I work on lithium metal oxides and sometimes measure their XAS data. XAS data show typical trend, i.e; first prominent peak related with metal-oxygen co-ordination shell and second prominent peak is associated with metal-metal co-ordination shell in my materials. I have noticed that in similar crystal structures Li2MO3-type (where M is transition metal), if metal belongs to 3d transition metal groups I get a single prominent metal-metal peak but for 5d transition metals, the metal-metal peak splits and its intensity also drops. I could not figure out the reason for the splitting of metal-metal peak in case of 5d metals. I have attached a PDF file in which calculated EXAFS spectra for Li2RuO3 (4d transition metal) and Li2PtO3 (5d transition metal) are shown and metal-metal (Pt-Pt) peak in Li2PtO3 shows clear splitting whereas metal-metal peak for Li2RuO3 does not split even though their "ATOMS" input files are very similar. I would appreciate if anybody could briefly explain the reason for metal-metal peak splitting in 5d metals or point me towards any literature. Attachment can be downloaded from the below link as well. https://www.dropbox.com/s/1m3kf764junuukk/Metal-Metal%20Peak%20Splitting%20i n%205d.pdf?dl=0 Thanks, Shoaib Muhammad Department of Energy Science Sungkyunkwan University (South Korea)

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Limit for number of data points in a file to be imported in Athena
by Kaustubh Priolkar 16 Sep '17

16 Sep '17

Hi! I have a QEXAFS data file with 12000 data points but Athena reads it only partially. Is there a limit on maximum number of data points in a file that Athena can import? Is there a way to increase the limit? Thanks in advance, Kaustubh Sent from Mail for Windows 10

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[IFEFIT]Chi(E) in version 0.9.25
by Michael Stockenhuber 15 Sep '17

15 Sep '17

Dear mailing list, Is there any way to save data as Chi( E),i.e., energy one column and chi(E) in the 2nd column? This was possible in the past and it would be great to have that to be able to import into excurv. Thank you for all the help and great programs Cheers Michael Prof. Michael Stockenhuber Chemical Engineering, School of Engineering Faculty of Engineering and Built Environment The University of Newcastle T +61 2 4985 4433 F +61 2 4921 9095 M + 61 (0) 450352239 Michael.stockenhuber(a)newcastle.edu.au<mailto:Michael.stockenhuber@newcastle.edu.au> President Catalysis Society of Australia www.catalysis.org.au<http://www.catalysis.org.au> Co-chair ACEME 2018 https://www.aiche.org/aceme2018 Co-chair ISHHC 2018 http://www.ishhc17.org

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How to use Artemis with feff85L
by José Carlos Conesa 14 Sep '17

14 Sep '17

Hi, I should like to use feff85L within Artemis (from Demeter 0.9.25), just to check in my system whether selfconsistency has a role in unifying E0 values (with feff 6, allowing different E0 for each scatterer leads to E0 differences >10 eV, which seems too much to me). I find that after loading the EXAFS data (from Athena) and a model (a .cif file containing Cu, Ce and O atoms), if I click Run Atoms and then Run Feff with feff6 as executable I get the usual set of paths that allow me doing a fit of the data, but if I try to use the feff85L.exe that comes with the Demeter software (by changing the feff executable in the File/Edit preferences menu), after clicking the Run Feff button (without including the SCF card) a bit of computation happens and after finishing it the path list is empty. ¿Any idea of the possible reason why I get no path list? Thanks in advance -- José C. Conesa Instituto de Catálisis y Petroleoquímica, CSIC Marie Curie 2, Madrid, Spain www.icp.csic.es Tel. (+34)915854766

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