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Title: EXAFS energy shift and structural parameters.

Abstract

In EXAFS analysis, the energy shift parameter is used to align the theoretical calculated spectrum to the energy grid of the measured spectrum. Unrealistically large energy shift values, sometimes in excess of 20 eV, are at times published in research articles. We therefore see the need for a concise discussion of the EXAFS energy shift parameter. This paper is intended as a learning tool for the proper alignment of theory to measured EXAFS spectra and proper interpretation of the energy shift parameter.

Authors:
; ;
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
973751
Report Number(s):
ANL/BIO/CP-119075
TRN: US201006%%964
DOE Contract Number:
DE-AC02-06CH11357
Resource Type:
Conference
Resource Relation:
Conference: 13th International Conference on X-ray Absorption Fine Structure (XAFS13); Jul. 9, 2006 - Jul. 14, 2006; Stanford, CA
Country of Publication:
United States
Language:
ENGLISH
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; ABSORPTION SPECTROSCOPY; X-RAY SPECTROSCOPY; ALIGNMENT; FINE STRUCTURE; SPECTRA; DATA ANALYSIS

Citation Formats

Kelly, S. D., Ravel, B., and Biosciences Division. EXAFS energy shift and structural parameters.. United States: N. p., 2007. Web. doi:10.1063/1.2644451.
Kelly, S. D., Ravel, B., & Biosciences Division. EXAFS energy shift and structural parameters.. United States. doi:10.1063/1.2644451.
Kelly, S. D., Ravel, B., and Biosciences Division. Mon . "EXAFS energy shift and structural parameters.". United States. doi:10.1063/1.2644451.
@article{osti_973751,
title = {EXAFS energy shift and structural parameters.},
author = {Kelly, S. D. and Ravel, B. and Biosciences Division},
abstractNote = {In EXAFS analysis, the energy shift parameter is used to align the theoretical calculated spectrum to the energy grid of the measured spectrum. Unrealistically large energy shift values, sometimes in excess of 20 eV, are at times published in research articles. We therefore see the need for a concise discussion of the EXAFS energy shift parameter. This paper is intended as a learning tool for the proper alignment of theory to measured EXAFS spectra and proper interpretation of the energy shift parameter.},
doi = {10.1063/1.2644451},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Mon Jan 01 00:00:00 EST 2007},
month = {Mon Jan 01 00:00:00 EST 2007}
}

Conference:
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  • In EXAFS analysis, the energy shift parameter is used to align the theoretical calculated spectrum to the energy grid of the measured spectrum. Unrealistically large energy shift values, sometimes in excess of 20 eV, are at times published in research articles. We therefore see the need for a concise discussion of the EXAFS energy shift parameter. This paper is intended as a learning tool for the proper alignment of theory to measured EXAFS spectra and proper interpretation of the energy shift parameter.
  • A general problem when fitting EXAFS data is determining whether particular parameters are statistically significant. The F-test is an excellent way of determining relevancy in EXAFS because it only relies on the ratio of the fit residual of two possible models, and therefore the data errors approximately cancel. Although this test is widely used in crystallography (there, it is often called a 'Hamilton test') and has been properly applied to EXAFS data in the past, it is very rarely applied in EXAFS analysis. We have implemented a variation of the F-test adapted for EXAFS data analysis in the RSXAP analysismore » package, and demonstrate its applicability with a few examples, including determining whether a particular scattering shell is warranted, and differentiating between two possible species or two possible structures in a given shell.« less
  • A general problem when fitting EXAFS data is determining whether particular parameters are statistically significant. The F-test is an excellent way of determining relevance in EXAFS because it only relies on the ratio of the fit residual of two possible models, and therefore the data errors approximately cancel. Although this test is widely used in crystallography (there, it is often called a 'Hamilton test') and has been properly applied to EXAFS data in the past, it is very rarely applied in EXAFS analysis. We have implemented a variation of the F-test adapted for EXAFS data analysis in the RSXAP analysismore » package, and demonstrate its applicability with a few examples, including determining whether a particular scattering shell is warranted, and differentiating between two possible species or two possible structures in a given shell.« less
  • No abstract prepared.
  • Substitution of the B component in the prototype AB{sub 5} type (LaNi{sub 5}) metal hydride alloys have resulted in their increased acceptance as anodes for rechargeable alkaline batteries. Recently substitution of the A component (La) for imparting properties such as increased corrosion resistance has received attention. This investigation deals with the role of Ce as a substituent for the La and its effect in terms of corrosion resistance. The alloys chosen have the general composition of La{sub x}Ce{sub 1-x}B{sub 5} (x = 1, 0.8, 0.5 and 0.25) where B is Ni{sub 3.55}CO{sub 0.75}Mn{sub 0.4}Al{sub 0.3} together with alloys containing themore » mischmetal (Mm) as the A component (both synthetic and commercial). Electrochemical cycling results show that Ce lowers the capacity loss in the alloys and that this effect is not a simple function of the extent of lattice expansion during hydriding as was previously suggested. Correlation of the electrochemical and XAS results show that capacity loss is directly related to the extent of Ni corrosion. Effect of Ce substitution seems to result in a stable Ce oxide hydroxide coating which imparts the corrosion resistance.« less