Structural and electronic properties of doped NiO from density functional theory and quantum Monte Carlo simulations

NiO is a prototypical strongly correlated oxide. According to band filling, it should be a metal, but correlations drive the ground state to an antiferromagnetic insulator. The general question of how doping affects the electronic – and chemical – structure of correlated oxides is of great fundamental interest, but also important for the realization of electronics,”Mottronics”, based on correlated materials. We are studying hole- and electron-doped NiO using density functional theory (DFT) methods and much more accurate quantum Monte Carlo simulations and compare our results directly with experimental results on high-quality thin films grown by molecular beam epitaxy. One surprising result is that DFT in all flavors we have used fails to properly account for the K-O bond distance, and underestimates it by over 0.3 A compared to analysis based on extended X-ray absorption fine structure. Preliminary results using QMC show much better agreement with experiments, indicating that correlation effects beyond DFT have a dramatic effect on the energy landscape around the dopant.