Adsorption of water on the MgO(001) surface

Physisorption of water on the MgO(001) surface has been investigated. New potentials between water and Mg2+ and between water and O2- have been constructed using intermolecular perturbation theory. The new potentials give an interaction energy of -65.4 kJ mol(-1) for isolated molecules on the surface, corresponding to a desorption enthalpy of 55 kJ mol(-1) at 220 K, in good agreement with an experimental estimate. Several different minimum-energy monolayer structures were investigated at a coverage of one water molecule per MgO unit. It was found that a pg(2 x 1) structure had a slightly lower equilibrium energy than the pg(3 x 2) structure found experimentally at about 200 K. It is suggested that differences in vibrational energy could account in part for the discrepancy between theory and experiment. (C) 1999 Elsevier Science B.V. All rights reserved.