In addition to the spatial and orientational densities of water, the interfacial hydrogen bonding also varies as a function of the distance from the metal. Figure maps the number of hydrogen bond donors and shows that the water molecules within the 1WL assemble into a network with a dual nature. First, at z ∼ 2 Å from the metal surfaces, there are more hydrogen-bonded molecules than in the bulk region (z ≳ 9 Å), while at z ∼ 3 Å the number of hydrogen bonds dips below the bulk value. Thus, the oscillation reflects the bilayer-type ⟨cos θ ⟩ distribution in Figure . Quantitatively, in the peak (dip) region the water molecules donate 1.50-1.75 (0.50-0.75) hydrogen bonds in average depending on the metal. Inspection of the distribution shows that at Au and Pt interfaces, water has the highest peak number of hydrogen bonds while Rh has the lowest dip below the bulk value.