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Title: Ab Initio Calculation of XAFS Debye-Waller Factors for Crystalline Materials

Abstract

A direct an accurate technique for calculating the thermal X-ray absorption fine structure (XAFS) Debye-Waller factors (DWF) for materials of crystalline structure is presented. Using the Density Functional Theory (DFT) under the hybrid X3LYP functional, a library of MnO spin--optimized clusters are built and their phonon spectrum properties are calculated; these properties in the form of normal mode eigenfrequencies and eigenvectors are in turn used for calculation of the single and multiple scattering XAFS DWF. DWF obtained via this technique are temperature dependent expressions and can be used to substantially reduce the number of fitting parameters when experimental spectra are fitted with a hypothetical structure without any ad hoc assumptions. Due to the high computational demand a hybrid approach of mixing the DFT calculated DWF with the correlated Debye model for inner and outer shells respectively is presented. DFT obtained DWFs are compared with corresponding values from experimental XAFS spectra on manganosite. The cluster size effect and the spin parameter on the DFT calculated DWFs are discussed.

Authors:
 [1]
  1. University of Texas-Pan American, Edinburg, TX 78539 (United States)
Publication Date:
OSTI Identifier:
21054571
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: 10.1063/1.2644449; (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 SPECTROSCOPY; CRYSTAL STRUCTURE; DEBYE-WALLER FACTOR; DENSITY FUNCTIONAL METHOD; EIGENFREQUENCY; EIGENVECTORS; FINE STRUCTURE; MANGANESE OXIDES; MULTIPLE SCATTERING; PHONONS; SPIN; TEMPERATURE DEPENDENCE; X-RAY SPECTRA; X-RAY SPECTROSCOPY

Citation Formats

Dimakis, Nicholas. Ab Initio Calculation of XAFS Debye-Waller Factors for Crystalline Materials. United States: N. p., 2007. Web. doi:10.1063/1.2644449.
Dimakis, Nicholas. Ab Initio Calculation of XAFS Debye-Waller Factors for Crystalline Materials. United States. doi:10.1063/1.2644449.
Dimakis, Nicholas. Fri . "Ab Initio Calculation of XAFS Debye-Waller Factors for Crystalline Materials". United States. doi:10.1063/1.2644449.
@article{osti_21054571,
title = {Ab Initio Calculation of XAFS Debye-Waller Factors for Crystalline Materials},
author = {Dimakis, Nicholas},
abstractNote = {A direct an accurate technique for calculating the thermal X-ray absorption fine structure (XAFS) Debye-Waller factors (DWF) for materials of crystalline structure is presented. Using the Density Functional Theory (DFT) under the hybrid X3LYP functional, a library of MnO spin--optimized clusters are built and their phonon spectrum properties are calculated; these properties in the form of normal mode eigenfrequencies and eigenvectors are in turn used for calculation of the single and multiple scattering XAFS DWF. DWF obtained via this technique are temperature dependent expressions and can be used to substantially reduce the number of fitting parameters when experimental spectra are fitted with a hypothetical structure without any ad hoc assumptions. Due to the high computational demand a hybrid approach of mixing the DFT calculated DWF with the correlated Debye model for inner and outer shells respectively is presented. DFT obtained DWFs are compared with corresponding values from experimental XAFS spectra on manganosite. The cluster size effect and the spin parameter on the DFT calculated DWFs are discussed.},
doi = {10.1063/1.2644449},
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}
}
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