Optical properties of point defects in SiO sub 2 from time-dependent density functional theory

We have studies the optical absorptions of a series of point defects in SiO sub 2 by means of time-dependent Density Funciotnla response theory, TD-DFT. The structure of the defects has been described with cluster models and atomic orbital basis functions. For each center the lowest singlet->singlet and singlet->triplet (for diamagnetic defects) and doublet->doublet (for paramagnetic defects) transitions have been considered.