title: Efficient simultaneous reverse Monte Carlo modeling of pair-distribution functions and extended x-ray-absorption fine structure spectra of crystalline disordered materials.
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.
authors.affiliation: Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, USA. Nemeth@ANL.Gov
authors.forename: Károly
authors.initials: K
authors.lastname: Németh
authors.forename: Karena W
authors.initials: KW
authors.lastname: Chapman
authors.forename: Mahalingam
authors.initials: M
authors.lastname: Balasubramanian
authors.forename: Badri
authors.initials: B
authors.lastname: Shyam
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Chupas
authors.forename: Steve M
authors.initials: SM
authors.lastname: Heald
authors.forename: Matt
authors.initials: M
authors.lastname: Newville
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Klingler
authors.forename: Randall E
authors.initials: RE
authors.lastname: Winans
authors.forename: Jonathan D
authors.initials: JD
authors.lastname: Almer
authors.forename: Giselle
authors.initials: G
authors.lastname: Sandi
authors.forename: George
authors.initials: G
authors.lastname: Srajer