| Abstract
| - A method has been developed which allows the simultaneousrefinement of X-ray powder diffractiondata and one or more EXAFS spectra from the same sample using a singleset of coordinates to describe the structure.The atomic positions are refined together with isotropic thermalfactors, peak shape and amplitude parameters, andthe EXAFS energy zeros for each absorption edge. The programdetermines the point symmetry and radial coordinatesof each site occupied by an atom for which EXAFS data are available,allowing a full multiple scattering calculationto be performed for each site. Mixed or partial occupancy of sitesis permitted. Where correlations between atomscan be calculated, as with copper for which Debye theory can be used,EXAFS mean-square displacements can bederived from the isotropic thermal factors, otherwise either thecorrelations or the EXAFS mean-square relativedisplacements must be introduced as separate variables. The methodpotentially allows us to accurately determinethe position of oxygen and other light atoms in materials where thediffraction pattern is dominated by heavy atoms,and to determine the occupancy of sites where elements of similarscattering amplitude are involved. Results areparticularly good where the EXAFS of several absorbing atoms areavailable.
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