First-principles study of the thermal reactions of H2 with germanosilicate optical fibers

Abstract

Abstract First-principles quantum chemical techniques are used to investigate the microscopic mechanisms for the thermal reactions of H 2 with germanosilicate optical fibers. In particular, accurate calculations including electron correlation effects have been performed on appropriate model systems to calculate activation barriers for the reactions of H 2 with Ge-O and Si-O bonds. Transition state studies for the two reactions clearly show that the activation barrier for Ge-O bond breaking is ≈ 0.5 eV lower in energy than that for the Si-O bond. Assuming similar pre-exponential factors, the reactions at the Ge site should be the dominant mechanism even at temperatures as high as 1000°C. This is consistent with the results from recent experimental observations.