ATOMISTIC SIMULATION OF THE EFFECT OF DISSOCIATIVE ADSORPTION OF WATER ON THE SURFACE-STRUCTURE AND STABILITY OF CALCIUM AND MAGNESIUM-OXIDE

Hydroxylation of the {100}, {110}, {111}, and {310} surfaces of MgO an d CaO by dissociative adsorption of water has been studied using atomi stic simulation techniques. We found that unstable surfaces with high surface energies tend to microfacet into steps of stable {100} planes, creating two possible sites for hydroxylation. As found experimentall y, the perfect MgO {100} surface is shown not to be amenable to hydrox ylation. However, on stepped {100} surfaces, modeled by the {310} and faceted {110} surfaces, adsorption is energetically favorable and pref erentially occurs at low-coordinated sites. The calculated hydration e nergies for CaO and MgO are in good agreement with experimental values where available.