One-Dimensional Zigzag Chain of Water Formed on a Stepped Surface

We determined the structure of water at step edges on the stepped Pt(211) = 3(111)-(100) surface using surface X-ray diffraction. Adsorbed water molecules form a chain with a zigzag configuration along the step line through hydrogen bonds. The chain comprises two types of water molecules. One is adsorbed on the top of the step atom and has a shorter Pt-O distance than that adsorbed on terrace sites, which indicates stronger adsorption at step edges. The other is displaced from the precise on-top sites and has an elongated Pt-O distance. The hydrogen-bonding configuration of the water chain is different from the tetrahedral arrangement of ice. The interaction of the water molecules with the surface distorts the hydrogen bonds in the water chain.