Kramers-Kronig and FEFF analysis for YBa₂Cu₃O_6.6

The DAFS f' and f'' functions were isolated using the Kramers-Kronig method and the resulting f' and f'' functions were splined to obtain the corresponding and functions. Because the and functions contain linear combinations of contributions from the Cu(1) and Cu(2) sites, simple weighted differences between pairs of reflections could be used to obtain the site-separated contributions. The site-separated Cu(1) and Cu(2) Fourier transform magnitudes obtained by calculating weighted differences of the pairs using the crystallographic weights in Table i, and then averaging over the pairs, are shown in Fig. 9. A FEFF calculation of the Fourier transform magnitudes expected for the separate Cu(1) and Cu(2) sites using the known YBa₂Cu₃O_6.6 structure are also shown. The agreement is very good and could probably be improved by allowing the crystallographic weights to vary slightly. These results clearly demonstrate the potential of EDAFS for site-selective short-range atomic structural studies.