Excitonic states in pure and impurity-doped magnesium oxide

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 S^2-- or Se^2--doped MgO show quite conclusively that the lattice response needs to be consistently incorporated with the defect electronic structure.