Influence of ligand field and correlation on the electronic structure of NiO and CoO from DFT+DMFT calculations

The intriguing physics and rich application potential of strongly correlated first-row transition metal oxide compounds result from the complex interplay of several factors that influence the electronic structure. To shed light on the effect of composition, structure, and correlation strength, we apply a well-established charge self-consistent combination of density functional theory and dynamical mean field theory, which has proven to give electron binding energies in good agreement to experimentally derived excitation spectra. For paramagnetic NiO and CoO, we analyze the effect of rock-salt and zincblende structures and their different ligand fields on the spectral functions. By varying the value of the interaction parameter U, different correlation strengths among the transition-metal 3d electrons are considered, as well as the effect of additionally accounting for correlations in the oxygen 2p orbitals by a self-interaction-correction pseudopotential scheme. It is shown that this combined DFT+sicDMFT approach leads to spectral functions and band gaps close to experimental data, thereby offering a time-efficient alternative to using a fully correlated model which would treat both, metal and oxygen ligand electrons within DFT+DMFT.