Excitonic states in pure and anion-impurity-doped MgO are investigated in several well-defined models using unrestricted Hartree-Fock (UHF)/icecap (ionic crystal with electronic cluster, automatic program) simulation procedures. The calculated excitation energies in pure MgO are in excellent agreement with the experiment. The results for ${\mathrm{S}}^{2\mathrm{-}}$- or ${\mathrm{Se}}^{2\mathrm{-}}$-doped MgO show quite conclusively that the lattice response needs to be consistently incorporated with the defect electronic structure.

• Received 18 January 1989

DOI:https://doi.org/10.1103/PhysRevB.39.12565