Importance of interatomic hole screening in core-level spectroscopy of transition metal oxides: Mn 3s hole states in MnO

Ab initio theoretical results are reported to determine the role of interatomic screening of the metal core hole in Mn $3s$ x-ray photoelectron spectra (XPS) of MnO. We present information that finally resolves the controversy about the relative importance of intra-atomic and interatomic effects to the XPS spectra of ionic manganese compounds. We focus on the transitions to high-spin $3s$ core hole states, using a nonorthogonal configuration interaction method. This method allows for a balanced treatment of configurations that involve different degrees of screening of the core hole. The differences between MnO and NiO are analyzed. Although at first glance the two XPS spectra seem to have similar features, the $3s$ hole final states have completely different characteristics. In MnO, interatomic screening of the core hole is found to play a minor role. This is in contrast with NiO, where the inclusion of interatomic screening of the metal core hole has been shown to be crucial for a proper explanation of the Ni $3s$ XPS. The main reason for the difference is an essentially atomic effect, namely the smaller electron affinity of Mn as compared to Ni. We have assigned the weak feature observed in the Mn $3s$ XPS spectrum of MnO at around 10 eV to be a charge-transfer-type high spin satellite.