Theoretical study on the electronic structures of various F centers in MgO crystals

Ab initio SCF-MO calculations were performed on low-lying electronic states of various F centers in MgO crystals by using embedded cluster models. Because a simple cluster model embedded with point charges alone gave poor results, we generated environmental potentials (EPs) in a spectral representation scheme for Mg(2+) and O(2-) ions and used them instead of point charges around the clusters under consideration. Using embedded cluster models with the EPs and point charges, we calculated the low-lying electronic states of various F centers in MgO. The calculated order in energy was found to be: the (1)A(1) state of the surface F center < the (1)E state of the surface F center < the (1)B(3u) State of the bulk M center (F aggregates) < the (1)T(1u) state of the bulk F center. The energy separation of the (1)E, (1)B(3u), and (1)T(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 rights reserved.