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Title: EXAFS Analysis with Self-consistent Atomic Potentials

Abstract

Theoretical EXAFS spectra generated by FEFF6 and FEFF8 are compared. As a test of the effect of charge transfer on EXAFS analysis, we examine the aqueous uranyl (UO{sub 2}{sup 2+}) ion. We find that the major difference between FEFF8 and FEFF6 is the edge energy position of approximately 5 eV. Modest changes in the forward focusing multiple scattering path of the uranyl resulting with FEFF8 produce a better model of the measured hydrated uranyl spectrum.

Authors:
;  [1]
  1. Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL 60439 (United States)
Publication Date:
OSTI Identifier:
21054574
Resource Type:
Journal Article
Resource Relation:
Journal Name: AIP Conference Proceedings; Journal Volume: 882; Journal Issue: 1; Conference: XAFS13: 13. international conference on X-ray absorption fine structure, Stanford, CA (United States), 9-14 Jul 2006; Other Information: DOI: 10.1063/1.2644452; (c) 2007 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; ABSORPTION SPECTRA; ABSORPTION SPECTROSCOPY; CATIONS; COMPUTER CALCULATIONS; COMPUTERIZED SIMULATION; EV RANGE; FINE STRUCTURE; LIQUIDS; MOLECULAR IONS; MULTIPLE SCATTERING; POTENTIALS; URANIUM COMPOUNDS; X-RAY SPECTRA; X-RAY SPECTROSCOPY

Citation Formats

Kelly, Shelly D., and Ravel, Bruce. EXAFS Analysis with Self-consistent Atomic Potentials. United States: N. p., 2007. Web. doi:10.1063/1.2644452.
Kelly, Shelly D., & Ravel, Bruce. EXAFS Analysis with Self-consistent Atomic Potentials. United States. doi:10.1063/1.2644452.
Kelly, Shelly D., and Ravel, Bruce. Fri . "EXAFS Analysis with Self-consistent Atomic Potentials". United States. doi:10.1063/1.2644452.
@article{osti_21054574,
title = {EXAFS Analysis with Self-consistent Atomic Potentials},
author = {Kelly, Shelly D. and Ravel, Bruce},
abstractNote = {Theoretical EXAFS spectra generated by FEFF6 and FEFF8 are compared. As a test of the effect of charge transfer on EXAFS analysis, we examine the aqueous uranyl (UO{sub 2}{sup 2+}) ion. We find that the major difference between FEFF8 and FEFF6 is the edge energy position of approximately 5 eV. Modest changes in the forward focusing multiple scattering path of the uranyl resulting with FEFF8 produce a better model of the measured hydrated uranyl spectrum.},
doi = {10.1063/1.2644452},
journal = {AIP Conference Proceedings},
number = 1,
volume = 882,
place = {United States},
year = {Fri Feb 02 00:00:00 EST 2007},
month = {Fri Feb 02 00:00:00 EST 2007}
}
  • Theoretical EXAFS spectra generated by FEFF6 and FEFF8 are compared. As a test of the effect of charge transfer on EXAFS analysis, we examine the aqueous uranyl (UO{sub 2}{sup 2+}) ion. We find that the major difference between FEFF8 and FEFF6 is the edge energy position of approximately 5 eV. Modest changes in the forward focusing multiple scattering path of the uranyl resulting with FEFF8 produce a better model of the measured hydrated uranyl spectrum.
  • The enhancement of the fusion reaction rate in high-density two-component plasmas that consist of deuterium (D) and high-{ital Z} material such as carbon (C) or titanium (Ti) has been investigated theoretically. Ion-ion correlation in high-density two-component plasmas is described by a hypernetted-chain (HNC) equation including Coulomb potential of bound electrons. To take into account the effects of bound electrons, we calculate the degree of ionization of atoms consistently with HNC equations by using the Thomas-Fermi model. The results show that the fusion reaction rate of the D-D interaction is enhanced by a factor from 2 to 4 because the strongmore » screening by the surrounding high-{ital Z} ions reduces an effective potential between two colliding deuteriums, and then the degree of ionization of high-{ital Z} materials is found to be important to determine the enhancement factors.« less
  • Inverse problem solving computation was performed for solving PDF (pair distribution function) from simulated data EXAFS based on data FEFF. For a realistic comparison with experimental data, we chose a model of the first sub-shell Mn-0 pair showing the Jahn Teller distortion in crystalline LaMnO3. To restore the Fourier filtering signal distortion, involved in the first sub-shell information isolated from higher shell contents, relevant distortion matching function was computed initially from the proximity model, and iteratively from the prior-guess during consecutive regularization computation. Adaptive computation of EXAFS background correction is an issue of algorithm development, but our preliminary test wasmore » performed under the simulated background correction perfectly excluding the higher shell interference. In our numerical result, efficient convergence of iterative solution indicates a self-consistent tendency that a true PDF solution is convinced as a counterpart of genuine chi-data, provided that a background correction function is iteratively solved using an extended algorithm of MEPP (Matched EXAFS PDF Projection) under development.« less