First-principles simulations of dissociated and molecular hydrogen adsorption on silicon oxide clusters

Equilibrium geometries, adsorption energies, and electronic properties of a hydrogen molecule on Si3On (n = 1-6) clusters have been investigated using density functional theory. The hydrogen molecule preferably dissociates and all H atoms bind to the 2-fold coordinated Si atom with dangling bonds in nearly a fixed direction for the smaller clusters. The dissociated H atoms favor binding to the terminal no-bridged O atoms to form the SiOH radical in the rhombus chain structures as the oxygen contents increase. We also report the interaction between Si3O4 cluster and multi-H2 molecules. Our results show that, at first, the added hydrogen molecules tend to dissociate and neutralize the dangling bonds. After all the dangling bonds are neutralized, the hydrogen begins to adsorb on the complex in molecules with a small adsorption energy. In addition, the infrared and Raman spectra are valuable in distinguishing among adsorption and dissociation of the H2 molecules on silicon oxide.