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

Re: [Ifeffit] Cumulant expansion fittings
by Patrick Kluth 26 Jan '09

26 Jan '09

Hi Matt, >Of course, XAFS *is* a one-dimensional probe, not a three-dimensional one. >At least ignoring for the moment the angular dependence of multiple >scattering, XAFS is sensitive to g(r) only. Sadly, this is sometimes >forgotten in the literature, and one sees attempts to distinguish >"sigma^2_perpendicular" and "sigma^2_parallel", which is a good sign of a >paper that is complete nonsense. I don`t agree with you in this point. To my understanding, because EXAFS is a one-dimensional probe and it measures the average over instantaneous inter-atomic distances, it is only sensitive to the motion relative to each other along the bond-direction - and thus measures sigma^2_parallel. Combined with XRD which measures the the atomic motion averaged over all directions one can then extract a "sigma^2_perpendicular". If we are talking about the same literature this point is well elaborated in there and I don`t think it is nonsense. Please correct me if I am wrong. Cheers, Patrick --------------------------------------------------------------------- Dr. Patrick Kluth Fellow, ARC Australian Research Fellow Department of Electronic Materials Engineering Research School of Physics and Engineering The Australian National University Canberra, ACT 0200 AUSTRALIA Phone: +61 2 6125 0358 Fax: +61 2 6125 0511 Mobile: +61 408 66 31 04 Email: patrick.kluth(a)anu.edu.au http://www.rsphysse.anu.edu.au/eme ---------------------------------------------------------------------

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small-screen version of Athena document
by Bruce Ravel 26 Jan '09

26 Jan '09

Hi, There is now a version of the Athena User's Guide which is intended for small-screen device (like my the new toy I got this weekend). Here is the URL: http://cars9.uchicago.edu/~ravel/software/doc/Athena/mobile/ This is very similar to the normal html version of the User's Guide, except for a few changes in layout to make it work better on a small screen. The mobile version is not perfect yet, but it is much more legible than the normal version. I have tested it mostly in Explorer on Windows Mobile 6. (I have also tested it under Opera for mobile devices, but I am not happy with how either version gets displayed there.) Hopefully this will be helpful for someone. Regards, B -- Bruce Ravel ------------------------------------ bravel(a)bnl.gov National Institute of Standards and Technology Synchrotron Methods Group at NSLS --- Beamlines U7A, X24A, X23A2 Building 535A Upton NY, 11973 My homepage: http://xafs.org/BruceRavel EXAFS software: http://cars9.uchicago.edu/~ravel/software/exafs/

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Query regarding measurement uncertainity
by Bindu R. 26 Jan '09

26 Jan '09

Dear all, I have one doubt regarding the measurement uncertainty in R- space (εR). In the manual it is written that εR is evaluated from the rms value of FT in the range 15-20 Å. My doubt is..... In case the FT in R-space does not extend up to the range mentioned above, then how does the fitting program choose the value of εR? Please clarify me this. With best regardsBIndu Dr.Bindu R. Visiting Fellow BG-37 DCMP&MS Tata Institute of Fundamental Research Homi Bhabha Road Colaba Mumbai-400 005 India Contact Number Lab- 022-2278 2256, 022-2278 2671 Mobile-919892536830 Add more friends to your messenger and enjoy! Go to http://messenger.yahoo.com/invite/

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FEFF calculations for Zeolite
by Feng Wang 23 Jan '09

23 Jan '09

Hi all, My colleague is trying to load Pt into the cages of the zeolite_LTA. It seems the crystallinity was destroyed with small Pt loading (<3%weight)according to the X-ray and e-beam diffraction. I suppose this is not sth new, but it looks intereting to understand the local structural structure with Pt loading, maybe by x-ray absorption or energy loss near-edge structure. Do you know how I should get the FEFF input file for this complex? Also please let me know if you have any relevant reports or your own results for exchange, I will appreciate that, thank you. Sincerely, Feng ==================================== National Institute for Nanotechnology 11421 Saskatachewan Drive Edmonton, Canada T6G 2M9

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Cumulant expansion fittings
by umesh palikundwar 22 Jan '09

22 Jan '09

Dear all, Cumulant expansion fittings are generally used, if there are more than one close shells of similar nearest neighbors (if I have understood it correctly). Third and fourth cumulants are used in the fittings to account for non-Gaussian distribution of the neighbors. I would like to known, can one use only fourth cumulant (i.e. without using the third cumulant) in the fittings? I will be highly grateful to get the answer to my query. Umesh _________________________________________________________________ What can you do with the new Windows Live? Find out http://www.microsoft.com/windows/windowslive/default.aspx

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SCF cards in EXAFS and SO2 of CO, Mn and Cu
by JeongEunSuk 18 Jan '09

18 Jan '09

Hello everyone I am using FEFF8.0 for the analysis of EXAFS. In FEFF, SCF card is for the calculation of self-consistent potential. I usually omitted SCF card for EXAFS. Is it right? Because the potential affects phase shift, I think that SCF card is also used in the analysis of EXAFS. which is correct, using SCF card or not in EXAFS? and I have another requirement. Could I know SO2 of Co, Mn and Cu? If anyone know those, would you show me? _________________________________________________________________ 메신저에서 클럽 이동도 한번에, 클럽을 운영하기 위한 것도 모두 제공! http://groups.live.com/

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book chapter
by Hashem Stietiya 16 Jan '09

16 Jan '09

Dr. Kelly, I would be thrilled if you could send me a copy. Thank you, Hashem Stietiya Louisiana State University -----Original Message----- From: ifeffit-bounces(a)millenia.cars.aps.anl.gov [mailto:ifeffit-bounces@millenia.cars.aps.anl.gov] On Behalf Of ifeffit-request(a)millenia.cars.aps.anl.gov Sent: Thursday, January 15, 2009 12:00 PM To: ifeffit(a)millenia.cars.aps.anl.gov Subject: Ifeffit Digest, Vol 71, Issue 16 Send Ifeffit mailing list submissions to ifeffit(a)millenia.cars.aps.anl.gov To subscribe or unsubscribe via the World Wide Web, visit http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit or, via email, send a message with subject or body 'help' to ifeffit-request(a)millenia.cars.aps.anl.gov You can reach the person managing the list at ifeffit-owner(a)millenia.cars.aps.anl.gov When replying, please edit your Subject line so it is more specific than "Re: Contents of Ifeffit digest..." Today's Topics: 1. Re: distinguishing between actual shells and artifacts (Kelly, Shelly) ---------------------------------------------------------------------- Message: 1 Date: Wed, 14 Jan 2009 13:58:21 -0700 From: "Kelly, Shelly" <Shelly.Kelly(a)uop.com> Subject: Re: [Ifeffit] distinguishing between actual shells and artifacts To: "XAFS Analysis using Ifeffit" <ifeffit(a)millenia.cars.aps.anl.gov> Message-ID: <5A8CCCCD35FC0946BE602D2F43C0218A7DF9FF(a)AZ18EV808.global.ds.honeywell.com> Content-Type: text/plain; charset="iso-8859-1" Hi Hashem, I show one method for doing this in my book chapter Figure 14-23 on page 431. (I feel a bit like a broken record). I will send you a copy if you want. Shelly > -----Original Message----- > From: ifeffit-bounces(a)millenia.cars.aps.anl.gov [mailto:ifeffit- > bounces(a)millenia.cars.aps.anl.gov] On Behalf Of Voegelin Andreas > Sent: Wednesday, January 14, 2009 9:57 AM > To: XAFS Analysis using Ifeffit > Subject: Re: [Ifeffit] distinguishing between actual shells and artifacts > > Hi Hashem > > You can copy-paste the respective EXAFS data in Athena and compare the > backtransforms over the first shell, the first+second shell, the second > shell. > > By comparison of the backtransforms with each other and with the measured > EXAFS, you can see where the second-shell contribution has its origin in > k-space (note that the backtransform is not corrected for the window > function). > > For instance, if the second-shell signal adds to the spectrum in the low-k > range (where noise should not be a problem), it is likely real and might > result, e.g., from multiple scattering among first-shell O atoms. If the > second-shell signal in the backtransform mainly contributes in the high-k > range (where noise or glitches may be a problem), you may be able to see > whether it falls together with obvious artefacts (such as glitches), or > whether the backtransform matches spectral features that you consider to > be real. > > Andreas > > ----------------------------------------------- > Andreas Voegelin, PhD > Soil Chemistry Group > Inst. of Biogeochemistry and Pollutant Dynamics > Dept. of Environmental Sciences > ETH Zurich > Universit?tstrasse 16, CHN F24 > CH-8092 Z?rich, Switzerland > Phone: +41 44 633 61 47 > Fax: +41 44 633 11 18 > E-Mail: voegelin(a)env.ethz.ch > www: http://www.ibp.ethz.ch/people/andreavo > > > > > -----Original Message----- > > From: ifeffit-bounces(a)millenia.cars.aps.anl.gov > > [mailto:ifeffit-bounces@millenia.cars.aps.anl.gov] On Behalf > > Of mstiet2(a)lsu.edu > > Sent: Mittwoch, 14. Januar 2009 14:12 > > To: ifeffit(a)millenia.cars.aps.anl.gov > > Subject: [Ifeffit] distinguishing between actual shells and artifacts > > > > Dear all, > > > > I am currently fitting first and second shells with Zn-O and > > Zn-Zn paths,respectively. I get second shell features that > > could be fit quite well, but I am not certain if they are > > actually second shell features or possibly artifacts. For > > some samples I get second shell features that I know should > > not be present. What criteria would you use to distinguish > > between artifacts and actual shells? > > > > Your assistance is appreciated. > > > > Hashem Stietiya > > > > Louisiana State University > > > > > > > > _______________________________________________ > Ifeffit mailing list > Ifeffit(a)millenia.cars.aps.anl.gov > http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit ------------------------------ _______________________________________________ Ifeffit mailing list Ifeffit(a)millenia.cars.aps.anl.gov http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit End of Ifeffit Digest, Vol 71, Issue 16 ***************************************

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difference between Zn-Zn/Fe and Zn-Fe paths
by Hashem Stietiya 16 Jan '09

16 Jan '09

Dear All, Is there a difference between fitting a second shell with two separate paths (Zn-Zn path and a Zn-Fe path) each with its own parameters and fitting that second shell with a combination of two paths (Zn-Zn/Fe)? When would I choose to do that latter, and how? I hope I made myself clear! Thanks, Hashem Stietiya Louisiana State University

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SCF and FMS radius
by Eugenio Otal 15 Jan '09

15 Jan '09

Hello, I am simulating the XANES spectra of a erbium atom in an interstitial site of ZnO. I needed a SCF radius of 9.75 (316 atoms) and FMS radius of 11.90 (599 atoms) to obtain no change in the simulated spectra (differences of 0.01% or less) Now I am trying to simulate Er(OH)3 and it is using SCF 10.90 (622 atoms) and I still haven found convergence, I will need more even larger radius for FMS. Does the XAS phenomena have this distances? Has this distances physical meaning? Thanks, euG 8<- - - - - - 8<- - - - - - 8<- - - - - - 8<- - - - - - Lic. Eugenio H. Otal E-mail: eotal(a)citefa.gov.ar eugenioh(a)gmail.com 8<- - - - - - 8<- - - - - - 8<- - - - - - 8<- - - - - -

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distinguishing between actual shells and artifacts
by mstiet2＠lsu.edu 14 Jan '09

14 Jan '09

Dear all, I am currently fitting first and second shells with Zn-O and Zn-Zn paths,respectively. I get second shell features that could be fit quite well, but I am not certain if they are actually second shell features or possibly artifacts. For some samples I get second shell features that I know should not be present. What criteria would you use to distinguish between artifacts and actual shells? Your assistance is appreciated. Hashem Stietiya Louisiana State University

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