Electron, hole and exciton self-trapping in germanium doped silica glass from DFT calculations with self-interactions correction
We performed density functional theory (DFT) calculations of electron, hole and exciton self-trapping in germanium doped silica glass to understand the refractive index change in these glasses induced by UV irradiation. The local structure relaxation and excess electron density distribution upon trapping of the above species were calculated. The results show that both trapped exciton and electron are highly localized on germanium ion and, to some extent, on its oxygen neighbors. Exciton self-trapping is found to lead to the formation of Ge E’ center and non-bridging hole center. Electron trapping changes the GeO4 tetrahedron structure into trigonal bi-pyramid with the majority of the excess electron density located along the equatorial line. Self-trapped hole is localized on bridging oxygen ions that are not coordinated to germanium atoms and leads to elongation of the Si-O bonds and change of the Si-O-Si bond angles. We did comparative study of standard DFT vs. DFT with a hybrid PBE0 exchange and correlation functional. The results show that the two methods give qualitatively similar relaxed structure and charge distribution for the electron and exciton trapping in germanium doped silica glass; however, only using the PBE0 functional reproduces the hole self-trapping. This research is supported by the Divisions of Chemical Science, Office of Basic Energy Sciences, US Department of Energy. This research was performed in part using the Molecular Science Computing Facility in the William R. Wiley Environmental Molecular Sciences Laboratory (EMSL) at the Pacific Northwest National Laboratory (PNNL). The EMSL is funded by DOE’s Office of Biological and Environmental Research. The pacific Northwest National Laboratory is operated by Battelle for the US Department of Energy.
- Research Organization:
- Pacific Northwest National Lab. (PNNL), Richland, WA (United States). Environmental Molecular Sciences Lab. (EMSL)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC05-76RL01830
- OSTI ID:
- 909459
- Report Number(s):
- PNNL-SA-50838; 9597; KC0301020; TRN: US0703890
- Journal Information:
- Nuclear Instruments and Methods in Physics Research. Section B, Beam Interactions with Materials and Atoms, 255(1 (SP ISS)):188-194, Vol. 255, Issue 1 (SP ISS)
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
ATOMS
BOND ANGLE
CHARGE DISTRIBUTION
E CENTERS
ELECTRON DENSITY
ELECTRONS
ELONGATION
EXCITONS
FUNCTIONALS
GERMANIUM
GERMANIUM IONS
GLASS
IRRADIATION
OXYGEN
OXYGEN IONS
REFRACTIVE INDEX
SILICA
TRAPPING
Environmental Molecular Sciences Laboratory