Periodic density functional theory calculations within the generalized gradient approximation for the exchange-correlation functional have been performed in order to study a water layer on the bimetallic Pd/Au(1 1 1) overlayer system. It turns out that a water bilayer in the H-down ice-Ih configuration is the most stable structure. Hydrogen and CO adsorption energies are influenced by less than 10% by the presence of the water bilayer. If an external negative electric field is applied, the stability of the H-down and H-up bilayer is reversed when the field is sufficiently strong. (c) 2005 Elsevier B.V. All rights reserved.