Cu K-edge XANES and Electronic Structure of Trivalent, Divalent, and Monovalent Cu Oxides

To elucidate the electronic structure of copper oxides with formally trivalent, divalent and monovalent Cu, x-ray absorption spectra were measured for NaCuO 2 , CuO and Cu 2 O by using synchrotron radiation. These XANES spectra were investigated by performing ab initio quantum chemical calculations based on the cluster-CI theory. The ground state of NaCuO 2 demonstrates strong covalent bonds between the Cu 3d and O 2p orbitals, resulting in small contribution of Cu(d 8 ) configuration and large contribution of Cu(d 9 ) configuration. The final-state effect in the Cu K-shell excited states of NaCuO 2 is similar to that of CuO, which explains that the overall structure in the spectrum of NaCuO 2 resembles that of CuO. On the other hand, the ground state of Cu 2 O demonstrates covalent bonds between the Cu 3d, Cu 4s and O 2p orbitals, resulting in a contribution of the Cu d 9 4s configuration. This configuration causes another type of final-state effect in the Cu K-shell excited states of Cu 2 O.