ATOMISTIC SIMULATION OF ADSORPTION OF WATER ON 3-COORDINATED, 4-COORDINATED AND 5-COORDINATED SURFACE SITES OF MAGNESIUM-OXIDE

Physisorption of water molecules on three-, four- and five-coordinated surface sites of MgO, modelled by the {100}, {310} and facetted {111} surfaces, has been studied using atomistic simulation techniques. It was found that physisorption is energetically favourable on all three different surface sites, but that it is most advantageous on the lower -coordinated sites, in agreement with experiment. However, it was foun d that coordination of the physisorbed water molecule to hydroxylated species stabilises physisorption of the five-coordinated surface sites . Intermolecular interactions between the physisorbed water molecules stabilise or destabilise the adsorbed layer, depending on geometry, bu t this effect is outweighed by the formation of a strong electrostatic interaction between the surface Mg ion and water oxygen ion.