It was noted that the observed reactivity of MgO with water was in apparent conflict with theoretical calculations which showed that molecular dissociation did not occur on a perfect (001) surface. First-principles total-energy calculations were performed which showed that a chemisorption reaction involving a reconstruction to form a (111) hydroxyl surface was strongly preferred, with ΔE = -90.2kJ/mol. It was concluded that protonation stabilized the otherwise unstable (111) surface and that this, not the bare (001), was the most stable surface of MgO under ambient conditions.

Water Chemisorption and Reconstruction of the MgO Surface. K.Refson, R.A.Wogelius, D.G.Fraser, M.C.Payne, M.H.Lee, V.Milman: Physical Review B, 1995, 52, 10823-6