Oxyden in MgO crystal. Local approach

The non-canonical localized Hartree–Fock orbitals of O$^{2-}$ ion in MgO crystal were calculated in the present paper with the help of the special variational procedure, the variational parameters being transferred from the wave function into the confining potential simulating the crystal environment. The cluster expansion for the crystal energy was employed and the summation over the crystal was made up to convergency. This procedure enabled one to incorporate in the natural way the intraionic correlation effects. The calculated cohesive properties of MgO are in good agreement with the experiment.