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SITE SELECTIVITY

Another important enhancement provided by DAFS is its site selectivity. Site selective DAFS measurements of crystallographically inequivalent Bragg reflections can be used to determine the XAFS-like information about the inequivalent sites within the unit cell even when these sites have the same atomic species. Because the DAFS intensity contains linear combinations of the contributions from the individual inequivalent sites, the specific site information can be obtained by resolving the individual contributions. In very favorable cases, some reflections will be dominated by a single site and the separation is easy [9]. In general, the individual contributions are not known and crystallographic procedures are needed. The tex2html_wrap_inline1946 superconductor is an attractive system to demonstrate site selectivity because the two inequivalent Cu sites play important roles in the material's superconductivity, and because there have been numerous previous XAFS studies of this system which can be compared with the DAFS results.