THEORETICAL-STUDY ON THE ELECTRONIC-STRUCTURES OF VARIOUS F-CENTERS IN MGO CRYSTALS

Ab initio SCF-MO calculations were performed on low-lying electronic s tates of various F centers in MgO crystals by using embedded cluster m odels. Because a simple cluster model embedded with point charges alon e gave poor results, we generated environmental potentials (EPs) in a spectral representation scheme for Mg2+ and O2- ions and used them ins tead of point charges around the clusters under consideration. Using e mbedded cluster models with the EPs and point charges, we calculated t he low-lying electronic states of various F centers in MgO. The calcul ated order in energy was found to be: the (1)A(1) state of the surface F center < the E-1 state of the surface F center < the B-1(3u) State of the bulk M center (F aggregates) < the T-1(1u) state of the bulk F center. The energy separation of the E-1, B-1(3u), and T-1(1u) states from the lowest state were 1.22, 2.46 and 4.05 eV, respectively, which explains the observed bands. (C) 1998 Elsevier Science B.V. All right s reserved.