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

Strange EXAFS oscillations, never seen before
by Rana, Jatinkumar Kantilal 19 Mar '17

19 Mar '17

Dear all, I observed strange EXAFS oscillations in my data up to about 1000 eV beyond the K-edge, I would like to share this situation with you and hope to get some feedback. Please find attached the athena project file of the data. The chemical composition of the material is (Fe0.5Cu0.5)Sn5. The EXAFS sample was prepared by taking the material equal to 2 absorption lengths at the Cu K-edge, mixing it with graphite and pressing into the pellet, which was sealed between the Kapton tape. The measurements were carried out at the Cu K-edge of the material in the transmission mode at the beamline 5BM of APS. Here are my concerns: (1) In the athena project file, the data files "Cu_S1_scan003" and "Cu_S1_scan004" are the two scans of the same sample measured one after the other. As can be seen, there are strong oscillations even at 1000 eV from the Cu K-edge, which is strange because generally EXAFS oscillations "wash out" as we go higher in energy. Nevertheless, the two scans appear reproducible. (2) Once I removed the sample and remeasured it after some time (because I did not believe the previous 2 scans), I found completely different data (i.e., data "Cu_S1_scan005"). (3) The Cu reference foil measured simultaneously along with the sample for each of these scans appear quite reproducible. I am puzzled as to what can contribute to such effects. I have never seen such effects before. We can rule out the possibility of beam damage, since I have measured up to 3 scans (25 min per scan) and they all look reproducible. However, once I remove the sample and remeasure it after some time to reproduce the previous 3 scans, the scan looks totally different. Also, we can rule out the chemical instability of the material, since the material is quite air-stable. I have measured a series of samples with this composition and all of them have the same effect. I would very much appreciate your feedback! Best regards Jatin ________________________________ Helmholtz-Zentrum Berlin für Materialien und Energie GmbH Mitglied der Hermann von Helmholtz-Gemeinschaft Deutscher Forschungszentren e.V. Aufsichtsrat: Vorsitzender Dr. Karl Eugen Huthmacher, stv. Vorsitzende Dr. Jutta Koch-Unterseher Geschäftsführung: Prof. Dr. Anke Rita Kaysser-Pyzalla, Thomas Frederking Sitz Berlin, AG Charlottenburg, 89 HRB 5583 Postadresse: Hahn-Meitner-Platz 1 D-14109 Berlin http://www.helmholtz-berlin.de

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[Question about XANES] Hello I'm a graduate student in Korea
by 김도엽(신소재공학과) 17 Mar '17

17 Mar '17

Hello I'm a graduate student at POSTECH in Korea. Currently, I obtained XANES spectra over a narrow energy range and looked through the Athena manual But, I'm kind of lost as to how exactly I'm supposed to normalize raw data which only has XANES spectra. It would be very generous of you if you help me figure this out Thank you Best wishes Doyoub Kim

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question mark in xanes plot athena
by Anna Smith 16 Mar '17

16 Mar '17

Hello, I am struggling with the normalization in Athena. When I plot u(E) and pre-ede and normalization ranges, I get a question mark on the plot instead of the normal cross (see below). Can you please help me solve this problem? Thanks in advance [cid:image001.jpg@01D29E50.91B6E320]

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Data export and coordination number
by Abhinav Prabhakar 13 Mar '17

13 Mar '17

Hello, As a new user, I have some questions related to the use of Athena and Artemis: i) Is it possible to extract the normalized/background corrected data from Athena (in E-,k- and R- space) and export it as numbers (to Excel perhaps)? ii) Using Artemis, how can coordination numbers (N) be expressed as 'guess' parameters (Artemis allows only numerical values for N)? Thank you. Regards, Abhinav Prabhakar (Mr.)

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Space group type in Artemis
by Abhinav Prabhakar 13 Mar '17

13 Mar '17

Hello, I have a question about the working of Artemis as a new user. Artemis does not recognize the space group B11b. When importing a cif file of a crystal with this symmetry, it sends a prompt message that the space group symbol cannot be recognized. As a result, I changed it to P11b and it works. But would this change any crystal information (for eg. Degen, Reff values) significantly? Thank you. Regards, Abhinav Prabhakar (Mr)

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APS/IIT Summer XAFS School
by Carlo Segre 06 Mar '17

06 Mar '17

Greetings: The 2017 APS/IIT SUmmer XAFS School will be held on July 9-13, 2017 in Chicago. This XAFS summer school is a continuation of the week-long summer school offered previously at the Advanced Photon Source; the venue will again be at IIT in Chicago, but will run Sunday-Thursday. Course material will cover fundamental and practical aspects of X-ray Absorption Fine Structure Spectroscopy: basics, sample preparation, experiment, theory, data analysis. One day of hands-on experiments will be carried out by participants at several APS beamlines, followed by a guided data analysis laboratory using Athena/iFEFFIT and other programs. Computers will be available for those participants attending without their own laptops. The target audience is graduate students, postdocs, and experienced scientists who are new to XAFS and want to use it in their own research. Space is available for up to 40 students. Instructors include: Dr. Steve Heald (ANL), Dr. Matt Newville (UChicago), Prof. Bruce Bunker (U. Notre Dame), Prof. Carlo Segre (IIT), Prof. Grant Bunker (IIT), and a number (positive, integer) of other experienced XAFS researchers also will participate. The cost of the course is $500 USD, which covers most but not all meals via an IIT meal card. Students will be responsible for their own housing (available on and off IIT campus) and travel to/from their home institutions. IIT is readily accessible by car, cab, and CTA train from O’Hare and Midway airports. Free time will be available most evenings for participants to visit Chicago attractions such as Grant Park, the Loop, Millennium Park, Lake Michigan; music, architecture, art, theater; Chinatown, White Sox, Field Museum, Shedd Aquarium, Adler Planetarium, and Navy Pier, restaurants, and pubs. Please email bunker(a)iit.edu with subject line “2017 XAFS School” for more information. -- Carlo U. Segre -- Duchossois Leadership Professor of Physics Interim Chair, Department of Chemistry Director, Center for Synchrotron Radiation Research and Instrumentation Illinois Institute of Technology Voice: 312.567.3498 Fax: 312.567.3494 segre(a)iit.edu http://phys.iit.edu/~segre segre(a)debian.org

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Relatively reduced ionization edge as opposed to oxidized !
by Ganesh Subramanian 01 Mar '17

01 Mar '17

Dear all, I have been running the FEFF to simulate for XANES spectra for the cobalamins (Vitamin B12 cofactors). The issue of interest is between three compounds - Methylcobalamin (Me-Cbl), Cyanocobalamin (CN-Cbl) and Hydroxocobalamin (OH-Cbl). Experimentally, Me-Cbl is supposed to the most reduced (in terms of the energy of onset of the rising absorption edge). OH-Cbl and CN-Cbl are supposed to be oxidized wrt Me-Cbl. (The official oxidation state of Cobalt for all the above three systems is +3). However, the simulations do no reflect this and it consistently seems to predict a reduced absorption edge for both OH-Cbl and CN-Cbl, in comparison to Me-Cbl. I checked the literature to confirm that the molecular coordinates that we are using as input (obtained after structure optimization using DFT - Gaussian09) is consistent with prior literature. I am wondering if there is anything related to FEFF that I miss understanding, to note why this is occurring. I am attaching the input files for the three models (these are all truncated to reduce the computational expense on DFT optimization) and the experimental and FEFF simulated spectra that I had obtained. Any help in understanding this seeming discrepancy is much appreciated. Thanking you, Ganesh

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downloading Demeter
by Bruce Ravel 01 Mar '17

01 Mar '17

To those who have noticed that Demeter has not been available for download in the last day or so: I use Amazon's S3 service to distribute the large installer files. You may have seen the news in the last 12 hours about a massive outage of that service, or you may have noticed that other internet resources that you use are unresponsive. There is nothing I can do to resolve this problem. Eventually Amazon S3 will come back on line and you will again be able to download Demeter. Please be patient and try again later. Regards, B Example news article: https://techcrunch.com/2017/02/28/amazon-aws-s3-outage-is-breaking-things-f… -- Bruce Ravel ------------------------------------ bravel(a)bnl.gov National Institute of Standards and Technology Synchrotron Science Group at NSLS-II Building 743, Room 114 Upton NY, 11973 Homepage: http://bruceravel.github.io/home/ Software: https://github.com/bruceravel Demeter: http://bruceravel.github.io/demeter/

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Limitations of maximum number of points in a data file in Athena
by Harishchandra Singh 01 Mar '17

01 Mar '17

Hi All, I have a query regarding limitation of maximum number of data points (or maximum size) of data file in to be imported in Athena. It would be great to hear form you all. Harish

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*****SPAM*****Acess download Athena sofware
by Joyce Ribeiro de Paula Santos 28 Feb '17

28 Feb '17

Hi folks My name is Joyce and I'm PhD' student in the Universidade de São Paulo, Brazil. Today, I tried to make a download of Athena software in the web site: http://bruceravel.github.io/demeter/ , but I couldn't make it. Could you provide me the link to download the athena software? Or give instructions how to make a download? Thanks -- Joyce Ribeiro de P Santos Graduada em Bacharelado em Ciências Biológicas - UFSCar Mestre em Microbiologia Agrícola - ESALQ/USP Doutoranda em Ciências Química na Agricultura e Ambiente - CENA/USP

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