Atomistic simulation of the surface carbonation of calcium and magnesium oxide surfaces

Computer modeling techniques using well-tested potential models to describe the interatomic interactions have been used to study the surface carbonation of the low index surfaces of magnesium and calcium oxides. We begin by studying the {100} surface and related, stepped {310} surface of these model oxides. Our results indicate that carbonation is indeed a favorable process, particularly enhanced by the inclusion of the step on the surface, and proceeds via incorporation into the surface. rather than mono- or bidentate adsorption above the surface. As the amount of surface carbonation is increased, surface energy lowers to a minimum, with calculated vibrational frequencies indicating the formation of a layer of carbonate material. In comparison to water adsorption, the majority of calcium oxide surfaces are predicted to compete favorably, whereas the magnesium equivalents show a greater stability from water. This is particularly apparent for the higher energy, polar {111} surface which forms a very stable hydroxylated surface.