Multiple-scattering analysis of $K$-edge x-ray-absorption near-edge spectrum of Y${\mathrm{Ba}}_2$${\mathrm{Cu}}_3$${\mathrm{O}}_7$

The copper $K$-edge x-ray-absorption near-edge structure (XANES) of Y${\mathrm{Ba}}_2$${\mathrm{Cu}}_3$${\mathrm{O}}_7$ has been analyzed by using the full multiple-scattering approach. By using the atomic coordinates of the orthorhombic oxygen-deficient perovskite structure, the absorption spectra of both Cu(1) and Cu(2) sites have been calculated. All features of the experimental Cu $K$-edge XANES spectrum can be simply interpreted as arising from one-electron transition to final states mainly determined by the atomic distribution in the large clusters of 40 atoms surrounding the Cu(1) and Cu(2) central absorbing atoms. The XANES spectra in this strongly anisotropic system are strongly polarization dependent; therefore the prediction of the polarized Cu $K$-edge spectra for a single crystal is reported. The role of the mixing of different configurations of the passive valence electrons on the Cu $K$-edge XANES is discussed.