Photoabsorption of the peroxide linkage defect in silicate glasses

First-principles quantum chemical techniques on cluster models have been us ed to investigate the photoabsorption of the peroxide linkage defect in sil icate glasses. The effects of geometry, basis sets, and cluster size have b een considered carefully to derive converged values for the low-lying excit ation energies. The lowest singlet-to-singlet transition is a weak absorpti on at 5.5 eV. A stronger valence absorption occurs at 6.8 eV. (C) 1999 Amer ican Institute of Physics. [S0021-9606(99)30739-X].