1ST-PRINCIPLES STUDY OF THE THERMAL-REACTIONS OF H-2 WITH GERMANOSILICATE OPTICAL FIBERS

First-principles quantum chemical techniques are used to investigate t he microscopic mechanisms for the thermal reactions of H-2 with german osilicate optical fibers. In particular, accurate calculations includi ng electron correlation effects have been performed on appropriate mod el systems to calculate activation barriers for the reactions of H-2 w ith Ge-O and Si-O bonds. Transition state studies for the two reaction s clearly show that the activation barrier for Ge-O bond breaking is a lmost-equal-to 0.5 eV lower in energy than that for the Si-O bond. Ass uming similar pre-exponential factors, the reaction at the Ge site sho uld be the dominant mechanism even at temperatures as high as 1000-deg rees-C. This is consistent with the results from recent experimental o bservations.