ELECTRONIC-STRUCTURE OF NIO AND RELATED 3D-TRANSITION-METAL COMPOUNDS

The electronic structure of the transition-metal compounds is discussed with nickel oxide (NiO) serving as the prime example. Other systems are also discussed, especially the high-temperature superconductors. The main finding of the review from the inspection of many data is that the electronic structure of these compounds is severely influenced by correlation of the Mott-Hubbard-type. Also in the metallic (itinerant) state these systems show aspects of correlations (satellites), which can only be explained in a one-ion model. It is this simultaneous occurrence of one-ion and one-electron features which makes the investigation of this class of materials fascinating but also frustrating, because at this point there is no unified theoretical approach available that would allow one to describe the electronic properties of these systems coherently.