A combined density functional theory and interatomic potential-based simulation study of the hydration of nano-particulate silicate surfaces

Density functional theory (DFT) calculations as well as interatomic potential-based simulations have been employed to study the adsorption of water at two α-quartz (0 0 0 1) surfaces. The different methods are found to be in agreement, both as to modes and energies of adsorption. When under-coordinated surface silicon and oxygen atoms are present, water adsorbs dissociatively at the surface, thereby annihilating dangling bonds by the formation of surface hydroxy groups. However, when the surface species are linked by Si–O–Si bridges and fully coordinated, water adsorbs associatively, releasing approximately 40 kJ mol−1. The comparison study shows that the use of complementary computational techniques is efficient in identifying and investigating low-energy surface features and behaviour. The potential model for hydrated silica performs sufficiently well to be suitable for use in further simulations of the hydration of a silicate nano-tube. Results of these calculations show that the side of the nano-tube is relatively resistant against dissociative chemisorption and silicon dissolution, but that the end of the nano-tube is highly reactive towards water and amenable to dissolution.