Reaction Mechanisms and Interfacial Behaviors of Sodium Silicate Glass in an Aqueous Environment from Reactive Force Field-Based Molecular Dynamics Simulations

Corrosion of silicate glasses in aqueous environment is common and it impacts many physical and chemical properties of these materials that have wide ranges of industrial and technological applications. However, the corrosion mechanisms of silicate glasses remain relatively poorly understood due to complicated interfacial reactions and transport behaviors. Here, we have employed molecular dynamics simulations with the recently developed reactive force field to investigate the sodium silicate glass and water interfacial reactions. Simulations up to 3 nano-seconds at four different temperatures were performed to study the key processes at the glass-water interface. The simulation results reveal three-stage interfacial reactions: (i) in the near-surface region, water diffusion and subsequent reactions with the nonbridging oxygen to form silanol groups are the dominating reactions; (ii) in the near-bulk region, the main reaction is silanol reformation through proton transfer; (iii) in the subsurface region (between the above two), both reactions were observed. It was also found that water transports in sodium silicate glasses mainly through two mechanisms: molecular water diffusion and proton transfer, with the former dominating in near-surface region and the latter dominating in all other regions. Acceleration of reactions and deeper water penetration were observed for higher temperature simulations, but by-products were observed for temperatures higher than 500 K.