Theory of resonant x-ray scattering and the establishment of the ab initio calculation method of the associated excited states

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We have studied the mechanism of the resonant x-ray scattering (RXS) from the microscopic viewpoint, and have obtained the following results :Elastic scattering(1)We have analyzed the RXS spectra at the magnetic superlattice spots around the Cu K edge in the antiferromagnet KCuF_3 and around the Ni K edge in NiO. Taking account of the spin-orbit interaction, we have carried out ab initio calculations within the local density approximation. We have explained various experimental facts, having clarified the mechanism of the orbital polarization on the zip band.(2)We have analyzed the RXS spectra at the magnetic superlattice spots around the Ga K edge in the antiferromagnet UGa_3 by carrying out the ab initio calculation with taking account of the spin-orbit interaction. We have clarified tha mechanism that the large orbital polarization in the 4p band of UGa3 arises from the large orbital moment of U atoms through the mixing between the Ga 4p states and the U 5f states. The experimental … More large spectral intensitieshave been explained naturally by the analysis.(3)We have analyzed the RXS spectra at the quadrupole ordering superlattice spots in CeB_6 on the basis of an atomic model including Ce4f-Ce4f interatomic interaction. The interference between the resonant scattering and the Thomson scattering found in the experiment have been well reproduced without assuming the lattice distortion.Inelastic scattering(1)We have analyzed the resonant inelastic scattering (RIXS) spectra around the Ge K edge on the basis of the ab initio calculation. The experimental spectra have been well reproduced, and the relation between the spectra and the band mapping has been clarified.(2)We have analyzed the RIXS spectra around the Cu K edge in La_2CuO_4 on the basis of the d-p model. Using the Hartree-Fock approximation together with the random phase approximation, we have calculated the spectra in good agreement with the experiment. We have clarified the mechanism for the move of the the spectral peak with varying final-state momenta. Less