Reactions and Diffusion of Water and Oxygen Molecules in Amorphous ${\mathrm{SiO}}_2$

Water and oxygen molecules determine many of the properties of amorphous ${\mathrm{SiO}}_2$ used in several technologies, but the underlying atomic-scale processes remain unresolved. We report results of first-principles calculations showing that a wide range of behavior is possible in an amorphous environment, including diffusion of the molecule as a whole and various reactions with the network. Experimental data including oxygen exchange reaction and radiation sensitivity are accounted for. The possibility of ${\mathrm{H}}_3{\mathrm{O}}^{+}$ formation as a source of positive charge is discussed.