Atomistic simulation of the dissociative adsorption of water on calcite surfaces

Atomistic simulation methods have been used to model the interaction of water with the {10 (1) over bar4} calcite surface and the energetics for the removal of carbonate groups in the presence of water. Electronic structure calculations show that associative adsorption of water is the energetically favored mode of adsorption on the {10 (1) over bar4} surface, that water is strongly bound to the surface, and that the atom-based simulations reproduce the energetics of adsorption. The use of atom-based molecular dynamics techniques on the calcite-water interface found that water loses its hydrogen-bond network when adsorbing on the surface and that it causes an oscillation of water density in the vicinity of the surface. Finally, we considered a possible reaction of the surface with water that would account for the presence of OH groups as observed experimentally on surfaces and would also constitute an initial step in the dissolution process. Our calculations suggest that carbonate groups at some step edges and low-index surfaces will dissociate water to form OH groups on the surface and release carbon dioxide but that this reaction does not take place on the undefective {10 (1) over bar4} surface.