Efficient simultaneous reverse Monte Carlo modeling of pair-distribution functions and extended x-ray-absorption fine structure spectra of crystalline disordered materials

The Journal of Chemical Physics
Károly NémethGeorge Srajer

Abstract

An efficient implementation of simultaneous reverse Monte Carlo (RMC) modeling of pair distribution function (PDF) and EXAFS spectra is reported. This implementation is an extension of the technique established by Krayzman et al. [J. Appl. Cryst. 42, 867 (2009)] in the sense that it enables simultaneous real-space fitting of x-ray PDF with accurate treatment of Q-dependence of the scattering cross-sections and EXAFS with multiple photoelectron scattering included. The extension also allows for atom swaps during EXAFS fits thereby enabling modeling the effects of chemical disorder, such as migrating atoms and vacancies. Significant acceleration of EXAFS computation is achieved via discretization of effective path lengths and subsequent reduction of operation counts. The validity and accuracy of the approach is illustrated on small atomic clusters and on 5500-9000 atom models of bcc-Fe and α-Fe(2)O(3). The accuracy gains of combined simultaneous EXAFS and PDF fits are pointed out against PDF-only and EXAFS-only RMC fits. Our modeling approach may be widely used in PDF and EXAFS based investigations of disordered materials.

References

Aug 22, 2001·Journal of Synchrotron Radiation·M Newville
Jun 22, 2005·Journal of Synchrotron Radiation·B Ravel, M Newville
Jan 21, 2010·Journal of Computational Chemistry·Károly NémethMichel Van Veenendaal
Aug 22, 2007·Journal of Physics. Condensed Matter : an Institute of Physics Journal·Matthew G TuckerQun Hui
Aug 22, 2007·Journal of Physics. Condensed Matter : an Institute of Physics Journal·C L FarrowS J L Billinge

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Citations

Feb 8, 2013·The Journal of Chemical Physics·Van-Thai Pham, John L Fulton
Oct 22, 2013·Journal of Physics. Condensed Matter : an Institute of Physics Journal·Martin T Dove, Gary Rigg

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Methods Mentioned

BETA
x-ray scattering
neutron
NMR
electron diffuse scattering
x-ray Absorption Near Edge Spectroscopy

Software Mentioned

FORTRAN
RMC PROFILE
ARTEMIS
IFEFFIT
PDFGUI
PDFGetX2
RMC
FEFF

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