Atomistic simulation of the free energies of dissolution of ions from flat and stepped calcite surfaces

Molecular dynamics simulations were used to describe the interaction of calcite flat and stepped surfaces with water. The calculations show that the disruptions of the water density caused by the presence of monoatomic step extend further in the direction normal to the surface than in the direction normal to the step edge. When vacancies were introduced, the disruption of the water density was dependent on both the type of vacancy and step. By performing a series of molecular dynamics simulations we were able to obtain free energy profiles of the dissolution of ions from flat and stepped surfaces. These results show that the type of surface that the ion is being dissolved from has a profound effect on the free energy of dissolution. In addition, our calculations suggest that the relationship between the overall free energy of dissolution and the number of crystal bonds to be broken is not linear, as normally assumed in dissolution models such as the solid-on-solid model.