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

Abstract

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 1A 1 state of the surface F center < the 1E state of the surface F center < the 1B 3u state of the bulk M center (F aggregates) < the 1T 1u state of the bulk F center. The energy separation of the 1E , 1B 3u , and 1T 1u states from the lowest state were 1.22, 2.46 and 4.05 eV, respectively, which explains the observed bands.