| Popis: |
Vitreous silica finds extensive use in fiber optic cables, which are currently considered to be used for sensor applications in high radiation fields in nuclear reactors. The darkening of the optical fibers in high radiation environments, resulting in the attenuation of signals, is a major concern for these applications. In this work, molecular dynamics (MD) simulations and first-principles electronic structure calculations are used to model and analyze the structural changes in glass fibers in high radiation environments and the corresponding changes in the electronic structure and optical properties. Besides the characterization of optically active defect structures in terms of vacancies or mis-coordinated atoms, a number of approaches for identifying and analyzing structural changes upon heating and irradiation in the amorphous system are analyzed. First-principles electronic structure calculations are used to correlate the structural properties of the defect structures to the resulting optical activity and to the resulting total attenuation. For this purpose, the Vienna Ab-initio Simulation Package (VASP) was used with HSE hybrid functional potentials, which allow accurate prediction of correct band gaps and optical properties. Computational results will be verified with the experimental setup, currently being developed in the Nuclear Engineering Department at OSU. |
