skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Non-MT Determination of X-Ray Absorption Cross-Section's Factorized Atomic Part in the Near-Edge Region. Application to Si K-Edge XANES Analysis in Beta-Zeolites

Abstract

An algorithm and code for the determination of the factorized atomic part of the absorption cross-section from experimental spectra in the XANES region were generated and tested on Al and Si K-edge XANES in reference compounds and applied to zeolite Beta with various Si/Al ratios. However, replacement of the theoretically determined background with the experimental absorption cross-section significantly improved the agreement with experiment. The spectral analysis showed that the XANES region can be used to extract detailed structural information when the Muffin-tin approximation can be avoided. Asymmetry in the silicon oxide tetrahedron was observed when increasing the aluminum content of the zeolite.

Authors:
; ;  [1];  [2]
  1. Physical Department of Rostov State University, Zorge str., 5, Rostov-on-Don, 344090 (Russian Federation)
  2. Institute for Chemical and Bioengineering, ETH Zurich, 8093 Zurich (Switzerland)
Publication Date:
OSTI Identifier:
21054569
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: 10.1063/1.2644446; (c) 2007 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; ABSORPTION SPECTRA; ABSORPTION SPECTROSCOPY; ALGORITHMS; ALUMINIUM; APPROXIMATIONS; ASYMMETRY; CROSS SECTIONS; MUFFIN-TIN POTENTIAL; SILICON; SILICON OXIDES; X RADIATION; X-RAY SPECTRA; X-RAY SPECTROSCOPY; ZEOLITES

Citation Formats

Bugaev, L. A., Avakyan, L. A., Latokha, Ya. V., and Bokhoven, J. A. van. Non-MT Determination of X-Ray Absorption Cross-Section's Factorized Atomic Part in the Near-Edge Region. Application to Si K-Edge XANES Analysis in Beta-Zeolites. United States: N. p., 2007. Web. doi:10.1063/1.2644446.
Bugaev, L. A., Avakyan, L. A., Latokha, Ya. V., & Bokhoven, J. A. van. Non-MT Determination of X-Ray Absorption Cross-Section's Factorized Atomic Part in the Near-Edge Region. Application to Si K-Edge XANES Analysis in Beta-Zeolites. United States. doi:10.1063/1.2644446.
Bugaev, L. A., Avakyan, L. A., Latokha, Ya. V., and Bokhoven, J. A. van. Fri . "Non-MT Determination of X-Ray Absorption Cross-Section's Factorized Atomic Part in the Near-Edge Region. Application to Si K-Edge XANES Analysis in Beta-Zeolites". United States. doi:10.1063/1.2644446.
@article{osti_21054569,
title = {Non-MT Determination of X-Ray Absorption Cross-Section's Factorized Atomic Part in the Near-Edge Region. Application to Si K-Edge XANES Analysis in Beta-Zeolites},
author = {Bugaev, L. A. and Avakyan, L. A. and Latokha, Ya. V. and Bokhoven, J. A. van},
abstractNote = {An algorithm and code for the determination of the factorized atomic part of the absorption cross-section from experimental spectra in the XANES region were generated and tested on Al and Si K-edge XANES in reference compounds and applied to zeolite Beta with various Si/Al ratios. However, replacement of the theoretically determined background with the experimental absorption cross-section significantly improved the agreement with experiment. The spectral analysis showed that the XANES region can be used to extract detailed structural information when the Muffin-tin approximation can be avoided. Asymmetry in the silicon oxide tetrahedron was observed when increasing the aluminum content of the zeolite.},
doi = {10.1063/1.2644446},
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}
}
  • Local environments of solutes in {beta}- and spinel Si{sub 6-z}Al{sub z}O{sub z}N{sub 8-z} are investigated by means of Al K x-ray absorption near-edge structure. The experimental spectra are found to be the same throughout the wide solubility range. This suggests that the local environments of Al are independent of the solute concentration. First-principles band-structure calculations are systematically made to interpret the experimental spectra. Effect of a core hole was included into the calculation. Theoretical spectra were obtained using variety of different model structures constructed by a set of plane-wave pseudopotentials calculations in our previous study [K. Tatsumi, I. Tanaka, H.more » Adachi, and M. Yoshiya, Phys. Rev. B 66, 165210 (2002)]. The numbers of models were 51 and 45 for both {beta} and spinel, respectively. They are classified and averaged according to the local atomic structure of Al solutes. The combination of experimental spectra and theoretical results can unambiguously lead to the conclusion that Al atoms are preferentially coordinated by O atoms in both {beta} and spinel phases. This is consistent with the conclusion obtained by the first-principles total-energy calculations. In the spinel phase, Al atoms are found to be located preferentially at the octahedral cationic site. This agrees with the conclusion in a recent report on the nuclear magnetic resonance experiment.« less
  • The N K-edge X-ray absorption near edge structure (XANES) spectra of the purine-containing nucleotide, guanosine 5{sup ′}-monophosphate (GMP), in aqueous solution are measured under various pH conditions. The spectra show characteristic peaks, which originate from resonant excitations of N 1s electrons to π* orbitals inside the guanine moiety of GMP. The relative intensities of these peaks depend on the pH values of the solution. The pH dependence is explained by the core-level shift of N atoms at specific sites caused by protonation and deprotonation. The experimental spectra are compared with theoretical spectra calculated by using density functional theory for GMPmore » and the other purine-containing nucleotides, adenosine 5{sup ′}-monophosphate, and adenosine 5{sup ′}-triphosphate. The N K-edge XANES spectra for all of these nucleotides are classified by the numbers of N atoms with particular chemical bonding characteristics in the purine moiety.« less
  • Initial results are reported on a new microprobe technique for determining Fe{sup 3+}/{Sigma}Fe ratios in Fe-bearing minerals. The technique is based on the energy shift of a pre-edge peak in X-ray absorption near-edge structure (XANES) spectra obtained using the synchrotron X-ray fluorescence microprobe. A linear relationship between pre-edge peak energy and iron oxidation state was observed for oxide and silicate standards. Reasonable iron oxidation state results were obtained for pallasitic olivine, acmite, altered magnetites, and synthetic wuestite. Direct measurements of Fe{sup 3+}/{Sigma}Fe in coexisting phases is feasible using this technique.
  • Curved-wave-multiple-scattering cluster calculations with the FEFF6 code were used to interpret experimental AlK-edge near-edge X-ray absorption fine structure (NEXAFS) spectra of various minerals and Y zeolites for energies {approximately}15 eV above threshold. Octahedral, tetrahedral, and square planar geometries of Al can be easily distinguished from each other utilizing characteristic features in the NEXAFS data. NEXAFS line shapes are used for determining the geometrical conformations of Al atoms in Y zeolites with one or more conformational geometries. In the H-Y zeolite, separate contributions to the NEXAFS from tetrahedrally and octahedrally coordinated Al atoms are identified. The differences in the octahedrally coordinatedmore » Al spectra in the H-Y zeolite compared with spectra for standard octahedrally coordinated Al compounds can be attributed to the presence of very small nonregular clusters of octahedrally coordinated Al dispersed over the zeolite. However, the presence of some pentacoordinated Al cannot be excluded.« less