Atomistic Simulation of Surface Selectivity on Carbonate Formation at Calcium and Magnesium Oxide Surfaces

Abstract

We report atom-level simulations of the surface selectivity and the resulting surface phase diagrams for the {100}, {110}, {111}, and {310} surfaces of CaO and MgO as a function of varying CO2 and H2O partial pressures. This work extends the traditional approach based on ab initio calculations, which can be time-consuming and costly for large systems, by using semiempirical atomistic simulations. The advantage of this approach is that very large numbers of calculations can be performed, thereby allowing a more effective search of the configurational space. The resulting free energies are used to generate the surface phase diagrams. The results indicate that the {100} surfaces of MgO and CaO show different dominant phases at atmospheric concentrations of gaseous water and carbon dioxide. The CaO surface forms a carbonated phase, whereas the MgO surface contains associatively adsorbed water. On the other hand, both {111} surfaces show the dominance of surface hydroxylation, effectively forming a layer of mi...