Crystal field calculations of energy levels of the Ni2+ ions in MgO

The electronic energy levels of six-fold coordinated Ni2+ ion in magnesium oxide MgO were calculated using the exchange charge model of crystal field theory. The calculated energetic positions of the Ni2+ levels match well the experimental spectrum. Inclusion of the spin-orbit (SO) interaction is compulsory to account for the first excited 3T2g state fine structure; however, it does not explain why out of four levels arising from the 3T2g state, only two are seen in the experimental spectra. One possible explanation to this fact can be advanced by invoking the Jahn–Teller effect.