Kinetic Monte Carlo Study on the Role of Heterogeneity in the Dissolution Kinetics of Glasses

The dissolution of silicate and other oxide glasses regulates many natural processes and plays an important role in many technological applications. Despite the fact that these glasses are inherently heterogeneous, current theories of glass dissolution exclusively rely on average descriptors of the structure or chemistry of the glass. The effect that spatial fluctuations in the local structure and chemical composition of a glass has on its dissolution kinetics is not well understood. Here, we use kinetic Monte Carlo (KMC) simulations to elucidate the role that heterogeneity plays in the dissolution kinetics of a glass model system. In single-phase particles, we find that heterogeneity, far from having a monotonic effect, can slow down or speed up the dissolution depending on the average extent of disorder of the glass. In two-phase particles, we find that the dissolution kinetics of phase-separated systems is governed by the less-soluble phase, while for well-mixed systems, the dissolution can be faster than that of the equivalent single-phase system because as the more soluble phase dissolves, it leaves behind a sparse structure of the less soluble phase which can then dissolve faster. We explain our findings based on both the mechanisms of dissolution observed in the KMC simulations and theoretical arguments.