Metal-insulator and magnetic transition of NiO at high pressures

The metal-insulator transition and magnetic collapse of NiO under high pressures have been studied with the hybrid density functional (HDF) and the general-gradient approximation (GGA). Our results show that even in the intermediate coupling regime GGA does not take the correlation effects into account appropriately. HDF predicts that the transitions occur at much higher pressures than GGA does. Band broadening, covalence, and crystal-field effects are responsible for the changes of the electronic structure under high pressures.