Quantum, classical, and multi-scale simulation of silica-water interaction: Molecules, clusters, and extended systems

Over the past 6years, we have engaged in a multi-faceted computational investigation of water-silica interactions at the fundamental physical and chemical level. This effort has necessitated development and implementation of simulation methods including high-accuracy quantum mechanical approaches, classical molecular dynamics, finite element techniques, and multi-scale modeling. We have found that water and silica can interact via either hydration or hydroxylation. Depending on physical conditions, the former process can be weak (<0.2eV) or strong (near 1.0eV). Compared to hydration, the latter process yields much larger energy gains (2-3eV/water). Some hydroxylated silica systems can accept more water molecules and undergo further hydroxylation. We have also studied the role of external stress, effects of finite silica system size, different numbers of water molecules, and temperature dependences.