Formation and Destruction of Si₆O₁₂ Nanostructures in the Gas Phase: Applications to Grain Nucleation and Water Generation

Silica grains are ubiquitous in both circumstellar media and rocky bodies and are vital to cosmic chemical processes, such as surface-catalyzed reactions and lunar water generation. Despite their pervasiveness, the chemical processes behind their formation and destruction, both of which are key to understanding their broader chemistry, are not fully established as of yet. Using chemically accurate CCSD(T)-F12/cc-pVTZ-F12 quantum chemical calculations, a reaction pathway including the possible bulk silica precursors Si3O6 and Si6O12 is mapped out herein. Through the reaction of SiO and H2O, the formation of such precursors is possible under circumstellar conditions. Expansion of this pathway may contribute to a complete understanding of silica and silicate chemistry throughout the universe. The constructed reaction pathway also shows that in the reverse reaction, processing of lunar silicates under the available photon flux of the sun can result in H2O production, following previous observations. The acceleration of H2O generation may be made possible through exposure of lunar silica to applied H2 in future aerospace ventures.