Covalency effect on cation 2p x-ray absorption spectroscopy in 3d transition-metal oxides

The influence of covalency on the L(2,3) spectral shape is studied for 3d transition-metal oxides. We present systematic calculations for cations with d(0) to d(8) configurations. Charge transfer leads to a more complex spectral shape and a change in balance between the main peaks. We also exhibit charge-transfer-induced high-spin-to-low-spin transition. We discuss some phenomenological models that have been suggested to account for covalency effects in the framework of ionic calculations, namely the increase in the crystal field possibly associated with a reduction in intracationic Slater integrals.