Correlations between Structural and Optical Properties of Peroxy Bridges from First Principles

Abstract

This work aims at addressing the issue of the optical signature of peroxy bridges by using first-principles methods that combine density functional theory, GW (where G and W stand for one-particle Green function and screened Coulomb potential, respectively), and the solution of a Bethe–Salpeter equation on a bulk amorphous SiO2 model. We demonstrate that the presence of bridges induces broad and weak absorption bands between 3.2 and 7.5 eV. By analyzing the Si–O–O–Si dihedral angle distributions and the corresponding electronic structure, we show that the low overlap between O 2p states involved in the optical transitions together with the dihedral angle site-to-site disorder are at the origin of this weak and broad absorption. Moreover, the energy difference between the two first optical transitions depends linearly on the energy difference between the two first occupied defect-induced electronic states, i.e., depends on the dihedral angle of the bridge. This behavior may explain the longstanding controversy regarding the optical signature of peroxy bridges in amorphous SiO2. Because the correlation is independent of the specific hosting hard material, the results apply whenever the dihedral angle of the bridge has some degree of freedom.

Creation of glass-characteristic point defects in crystalline SiO2 by 2.5 MeV electrons and by fast neutrons

“…In the same time, the data discussed in the previous section indicate that at least 10 18 cm −3 oxygen vacancies exist in the 10 19 e − / cm 3 irradiated crystal. Different to the case of glassy SiO2 [17], in the nearly intact crystal lattice of electronirradiated α-quartz the displaced oxygen atom evidently does not dimerize to form interstitial O2, but interacts instead with a normal "bridging"oxygen and forms a peroxy linkage (Si-O-O-Si bond), as predicted by most calculations, e.g., [45,46]. It is calculated that O2 molecule in α-quartz can be located in the structural channels along the c-axis, forms an angle of 51° between OeO direction and c-axis, however, it is strongly confined and causes a distortion of the surrounding quartz lattice [47].…”

Aggregation of ODC(I) and POL Defects in Bismuth Doped Silica Fiber

“…The unoccupied defect states for the bismuth-doped silica glass model with the ODC(I) defect are 0.55 eV and 2.45 eV in Figure 3 a. According to Figure 3 b [ 41 , 42 , 43 ], for the bismuth-doped silica glass model with POL defect, the unoccupied defect states appear at 1.14 eV and 3.0 eV. When the POL defect and ODC(I) defect aggregate in the bi-doped silica optical fiber, the unoccupied defect states can be seen in Figure 3 c at 0.2 eV and 0.42 eV.…”

Optical Absorption of Excimer Laser‐Induced Dichlorine Monoxide in Silica Glass and Excitation of Singlet Oxygen Luminescence by Energy Transfer from Chlorine Molecules

“…This is possible, either if O 2 and Cl 2 are paired (e.g., in very large interstitial voids), contrary to the random‐distribution discussed earlier, or if the laser photolysis‐generated O atoms are mobile enough to travel longer paths to distant Cl 2 molecules. It is generally agreed [ 37 ] that thermalized O atom diffuses by exchange with network O atoms, and forms a peroxy linkage SiOOSi. This diffusion is very slow at the room temperature.…”