Atomistic kinetic Monte Carlo modelling of crystal dissolution: Mechanisms and dynamics

Dissolution of minerals is a complex process that not only depends on the nature of the material, but also on its topography and the equilibrium with the solution1. In the case of cements, for instance, understanding the dissolution of alite and belite is of great importance from a technological point of view. In this sense, atomistic Kinetic Monte Carlo (KMC) simulations have been already employed in different fields of geochemistry to investigate the dissolution of materials at the nano-micro-scales. Unfortunately, current models usually assume far equilibrium conditions2,3 and fail to capture the dissolution mechanisms that take place close to chemical equilibrium between the dissolved ions in and the material. In order to account for the subtle reversible mechanisms that take place close to equilibrium, the commonly used KMC model, in which an atom in the material has a dissolving probability, is further complemented with another equivalent equation which also considers the probability of an atom from the solvent to enter the material. The method was tested in a general Kossel crystal, and to the best of our knowledge it is capable for the first time to reproduce the different mechanisms described in the literature as a function of the free energy and their dissolution flux. This is a general study applicable to any dissolving material, but with clear impact in cement materials where large changes in the free energy take place in short periods of time.