Large-cluster-model analysis of Cu 2p X-ray absorption spectrum of LaCuO₃

The double-peak feature in the Cu 2p photoabsorption line shape of LaCuO₃ is discussed on the basis of large-cluster-model calculations. Owing to the large covalency in LaCuO₃, the photoabsorption at a particular Cu site triggers the electronic excitation at neighboring Cu sites. The excitation energy at the distant Cu sites contributes to the energy separation of the two peaks in the Cu 2p absorption appreciably. Therefore the photoabsorption final states in LaCuO₃ cannot be simulated by a single-site cluster model,CuO₆, which is in clear contrast to the divalent transition-metal monoxides.