Hi everyone, I am new to EXAFS and have been working with Athena to process my data and trying to fit it with Artemis. I have LIII edge EXAFS data from monometallic carbon supported Pt, Re and bi-metallic PtRe nanoparticles (1-3nm). My objective to perform a first coordination shell fit, and i have been successful with the monometallic data and reference samples (Pt and Re foils and salts). Unfortunately success with PtRe bimetallics has been limited so far, and I can not get a good fit with reasonable delEo values. Did anyone work with platinum/rhenium before and can offer some helpful advice? The literature says that even though the backscattering properties of Pt and Re are similar (given their proximity on the periodic table), they should still be distinguishable with k0-weighted fitting. I was also if its possible to use Athena or Artemis to extract the back-scattering properties of Pt and Re from reference samples, and use these properties in fitting a Pt-Re path. Thank you very much for your help -Ed Kunkes Graduate Student University of Wisconsin-Madison Chemical Engineering
On Sunday 15 April 2007 12:40, Edward L. Kunkes wrote:
Hi everyone,
I am new to EXAFS and have been working with Athena to process my data and trying to fit it with Artemis. I have LIII edge EXAFS data from monometallic carbon supported Pt, Re and bi-metallic PtRe nanoparticles (1-3nm). My objective to perform a first coordination shell fit, and i have been successful with the monometallic data and reference samples (Pt and Re foils and salts). Unfortunately success with PtRe bimetallics has been limited so far, and I can not get a good fit with reasonable delEo values. Did anyone work with platinum/rhenium before and can offer some helpful advice? The literature says that even though the backscattering properties of Pt and Re are similar (given their proximity on the periodic table), they should still be distinguishable with k0-weighted fitting.
I don't personally have experience with a system quite like that. I did spend a fruitless couple of months a few years back trying to get something useful out of an Fe/Ga alloy with little success. The issue of their proximity is serious, but you can throw the whole bag of Ifeffit tricks at the problem. Use k-weights. Use multiple data set fits and data from both edges. Use temperature to help break the correlations between sigma^2 and amplitude. Use clever math expressions. It doesn't seem undoable to me.
I was also if its possible to use Athena or Artemis to extract the back-scattering properties of Pt and Re from reference samples, and use these properties in fitting a Pt-Re path.
This has been on my list of things to do for a long time. See http://cars9.uchicago.edu/iffwiki/HoraeToDoList and scroll to the end of the page. That said, I would need to be convinced that doing so is preferable to using Feff for EXAFS analysis (with the exception of a scattering geometry that involves an intervening hydrogen atom). B
I was also if its possible to use Athena or Artemis to extract the back-scattering properties of Pt and Re from reference samples, and use these properties in fitting a Pt-Re path.
We did a similar procedure (extracting back scattering properties from reference samples), although with FEFFIT, which is the predecessor of IFEFFIT. It should be also done by IFEFFIT by back Fourier transforming the reference samples and extracting amplitude and phases - they can then be combined in the "corrected" EXAFS equation which can be fit to the data by Artemis - with modified amplitude and phase factors. Here is the reference: A. I. Frenkel, M. Vairavamurthy, and M. Newville, A study of the coordination environment in aqueous cadmium-thiol complexes by EXAFS spectroscopy: experimental vs. theoretical standards J. Synchrotron Rad., 8 , 669-771 (2001). The link to the PDF is here: http://pubweb.bnl.gov/users/frenkel/www/EXP-FEFF/thiols.pdf Anatoly
participants (3)
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Anatoly Frenkel -
Edward L. Kunkes -
Ravel, Bruce D.