Abstract
The electronic structure of oxygen-vacancy defects (F, and centers) in MgO crystals has been studied within local-density theory, using the self-consistent mixed-basis pseudopotential techniques. The defects were modeled within a supercell having a volume 8 times that of the perfect MgO crystal. The band structure, density of states, charge-density contours, and total energy were calculated as a function of lattice relaxation. The partial density of states shows that each of the F-type centers introduces impurity states into the band gap as well as near the conduction-band edge of MgO. The total energy was calculated as a function of relaxation of the nearest-neighbor shell of ions. For F centers, the lowest-energy configuration was found to be a small inward relaxation of the nearest ions toward the vacancy site. For and centers, the lowest total energies correspond to a small outward relaxation of the ions away from the vacancy site. The electronic structure of hydrogen impurities ( and substitutional defects) in MgO was also investigated using the same approach. These impurities contribute defect states within and below the oxygen p bands as well as near the conduction-band edge of MgO. The lowest-total-energy configurations of both and substitutional defects correspond to a slight outward relaxation of the nearest -ion shell.
- Received 14 August 1989
DOI:https://doi.org/10.1103/PhysRevB.41.3211
©1990 American Physical Society