Structure and energetics of hydroxylated silica clusters, (SiO2)M(H2O)N, M=8,16 and N=1-4: A global optimisation study

The low energy isomer spectrum of hydroxylated silica clusters, (SiO2)M(H2O)N, is investigated using global optimisation with an empirical potential and ab initio structural and energetic refinement. The cases M = 8, 16 and N = 1 - 4 are considered in gas phase with respect to their relative energetic stabilities, reaction energies (relative to hydroxylation and condensation) and geometries. All hydroxylation reactions and condensation reactions are found to be energetically downhill, with the former becoming progressively less favourable with increasing hydroxylation. Hydroxylation also appears to affect the structures of smaller anhydrous clusters more than larger ones.