A study was made of the structure and spectroscopic properties of paramagnetic non-bridging O hole centers and of Eγ’ centers, at hydroxylated silica surfaces, by using density functional theory and an embedded-cluster model. In order to investigate the influence of the local environment upon the defect properties, 3 crystalline polymorphs of SiO2 were considered: edingtonite (100), β-cristobalite (111) and α-quartz (00▪1) surfaces. The calculations reproduced essential properties of the centers. The g-tensor and the optical transitions between well-localized defect states were in excellent agreement with experimental data for the silica surface. The hyperfine coupling constants agreed well with the experimental findings. The overall absorption spectra were in qualitative agreement with experiment.

Optical and EPR Properties of Point Defects at a Crystalline Silica Surface - ab initio Embedded-Cluster Calculations. L.Giordano, P.V.Sushko, G.Pacchioni, A.L.Shluger: Physical Review B, 2007, 75[2], 024109 (9pp)