Copper(110) surface in thermodynamic equilibrium with water vapor studied from first principles

The adsorption of water monomers, small water clusters, water chains and water thin films on the Cu(110) surface is studied by density-functional theory (DFT) as well as using a semi-empirical scheme to include dispersion forces (DFT-D). Among the cluster structures, tetramers are most favorable. The calculated surface phase diagrams show that out of the multitude of Cu(110)-adsorbed water structures studied here (and proposed in earlier experimental and theoretical works) only monolayers resembling water ice, water-hydroxyl group layers stabilized by Bjerrum defects, and – in a narrow range of the water chemical potential – chains assembled from water pentagons are thermodynamically stable. The inclusion of van der Waals interaction increases the calculated adsorption energies, but has only minor consequences for the energetic ordering of adsorption geometries. It increases the calculated desorption temperatures from 60 K in low pressures until 150 K in near ambient pressures.