Electronic Strucure and Final???State Effects in Nd2CuO4, La2CuO4, and Ca2CuO3 Compounds by Multiple???Scattering Theory at the Copper K Edge

We present a theoretical analysis, based on the zeroth-order approximation of the multichannel multiple-scattering theory, of the x-ray-absorption spectra of Nd2CuO4, La2CuO4, and Ca2CuO3 compounds at the copper K edge. Single channel theoretical calculations have been made using atomic clusters large enough to be sure that all one-electron features have been correctly described. On this basis the presence of both 3d9 and 3d10L_ configurations in the ground state has been found essential to obtain good agreement between experimental data and theoretical calculations in the case of Nd2CuO4 and Ca2CuO3. Conversely, the best agreement with the La2CuO4 data has been obtained by taking into account only the 3d10L_ configuration in the final state. We briefly comment on this finding.