We study the adsorption of water on MgO surfaces with the Car-Parrinello method. Our simulation shows that an ${\mathrm{H}}_2$O molecule in the proximity of a perfect (001) surface is physisorbed. The binding energy is rather small and the molecule desorbs at modest temperatures. We also simulated a stepped surface. On this surface the dissociation of water proceeds very rapidly. Our simulation is the first of this kind and agrees with experimental evidence.

• Received 25 February 1994

DOI:https://doi.org/10.1103/PhysRevLett.73.504