Modelling glass dissolution with a Monte Carlo technique

We present a Monte Carlo simulation method for modelling glass dissolution in aqueous solutions. This simulation method is consistent with transition state theory, and therefore also with the glass dissolution rate law, used for instance in the Grambow model. The simulation method allows to add dynamics (kinetics) to the existing thermodynamic models for glass dissolution. Using this method, it is possible to model non stoichiometric dissolution of the glass. Besides, we introduce a simple, first version of a model in which we use the simulation method. In this model, we approximate the glass by a lattice. We assume that the glass contains two components: a network former and a network modifier. Bonds between two network formers are assumed to be much stronger than any other bond in the system. We observe that above a threshold value for the concentration of network modifiers, the glass dissolves fast. No surface layer develops and the dissolution rate is constant (linear stoichiometric dissolution). Below this threshold, the glass is more durable and surface layers are formed. As time goes on, the thickness of the surface layers grows. The dissolution of the glass is not stoichiometric. This behaviour agrees with experimental results.