The atomic-start description of NiO
  We have calculated magnetic properties and the electronic structure of NiO both in the paramagnetic and in magnetically-ordered state as well as zero-temperature properties and thermodynamics within the strongly-correlated crystal-field approach. It is in agreement with a Mott's suggestion that NiO is an insulator due to strong electron correlations. We have quantified crystal-field, spin-orbit and magnetic interactions of the Ni2+ ion in NiO. We have obtained that E_dd >> E_CF(=2.0 eV) >> E_{s-o}(=0.29 eV) > E_mag(=0.07 eV). The orbital moment of 0.54 mu_B amounts at 0 K, in the magnetically-ordered state, to about 20% of the total moment (2.53 mu_B). Our studies indicate that it is the highest time to "unquench" orbital magnetic moment in 3d solid-state physics and the necessity to take always into account strong intra-atomic correlations among d electrons and the intra-atomic spin-orbit coupling.   Pacs: 75.25.+z, 75.10.Dg   Keywords: Crystalline Electric Field, 3d oxides, magnetism, spin-orbit coupling NiO 
R.J. Radwanski and Z. Ropka