H2O adsorption on Ni(100): Evidence for oriented water dimers

H₂O adsorption on clean Ni(110) surfaces at T ≦ 150 K leads at coverages below $\text{θ ? 0.5}$ to the formation of chemisorbed water dimers, bound to the Ni substrate via both oxygen atoms. The linear hydrogen bond axis is oriented parallel to the [001] surface directions. With increasing H₂O coverage $\text{(θ ≧ 0.5)}$, the accumulation of further hydrogen bonded water molecules induces some modification of the dimer configuration, producing at $\text{θ ? 1}$ a two-dimensional hydrogen bonded network with a slightly distorted ice lattice structure and long range order.