TY - JOUR
T1 - A combined fit of total scattering and extended X-ray absorption fine structure data for local-structure determination in crystalline materials
AU - Krayzman, V.
AU - Levin, I.
AU - Woicik, J. C.
AU - Proffen, Th
AU - Vanderah, T. A.
AU - Tucker, M. G.
PY - 2009
Y1 - 2009
N2 - Reverse Monte Carlo (RMC) refinements of local structure using a simultaneous fit of X-ray/neutron total scattering and extended X-ray absorption fine structure (EXAFS) data were developed to incorporate an explicit treatment of both single- and multiple-scattering contributions to EXAFS. The refinement algorithm, implemented as an extension to the public domain computer software RMCProfile, enables accurate modeling of EXAFS over distances encompassing several coordination shells around the absorbing species. The approach was first tested on Ni, which exhibits extensive multiple scattering in EXAFS, and then applied to perovskite-like SrAl1/2Nb1/2O3. This compound crystallizes with a cubic double-perovskite structure but presents a challenge for local-structure determination using a total pair-distribution function (PDF) alone because of overlapping peaks of the constituent partial PDFs (e.g. Al - O and Nb - O or Sr - O and O - O). The results obtained here suggest that the combined use of the total scattering and EXAFS data provides sufficient constraints for RMC refinements to recover fine details of local structure in complex perovskites. Among other results, it was found that the probability density distribution for Sr in SrAl1/2Nb1/2O3 adopts Td point-group symmetry for the Sr sites, determined by the ordered arrangement of Al and Nb, as opposed to a spherical distribution commonly assumed in traditional Rietveld refinements.
AB - Reverse Monte Carlo (RMC) refinements of local structure using a simultaneous fit of X-ray/neutron total scattering and extended X-ray absorption fine structure (EXAFS) data were developed to incorporate an explicit treatment of both single- and multiple-scattering contributions to EXAFS. The refinement algorithm, implemented as an extension to the public domain computer software RMCProfile, enables accurate modeling of EXAFS over distances encompassing several coordination shells around the absorbing species. The approach was first tested on Ni, which exhibits extensive multiple scattering in EXAFS, and then applied to perovskite-like SrAl1/2Nb1/2O3. This compound crystallizes with a cubic double-perovskite structure but presents a challenge for local-structure determination using a total pair-distribution function (PDF) alone because of overlapping peaks of the constituent partial PDFs (e.g. Al - O and Nb - O or Sr - O and O - O). The results obtained here suggest that the combined use of the total scattering and EXAFS data provides sufficient constraints for RMC refinements to recover fine details of local structure in complex perovskites. Among other results, it was found that the probability density distribution for Sr in SrAl1/2Nb1/2O3 adopts Td point-group symmetry for the Sr sites, determined by the ordered arrangement of Al and Nb, as opposed to a spherical distribution commonly assumed in traditional Rietveld refinements.
KW - Extended X-ray absorption fine structure (EXAFS)
KW - Local structure determination
KW - Reverse Monte Carlo refinement
KW - X-ray/neutron total scattering
UR - http://www.scopus.com/inward/record.url?scp=70349333043&partnerID=8YFLogxK
U2 - 10.1107/S0021889809023541
DO - 10.1107/S0021889809023541
M3 - Article
AN - SCOPUS:70349333043
SN - 0021-8898
VL - 42
SP - 867
EP - 877
JO - Journal of Applied Crystallography
JF - Journal of Applied Crystallography
IS - 5
ER -