Issue Date: March 16, 2009
Ice Forms From Water Pentagons, Too
Water molecules typically arrange into hexagons to form ice. Now, investigating ice formation on a copper surface, a group led by Angelos Michaelides of the London Center for Nanotechnology has found that ice can also form from water pentagons (Nat. Mater., DOI: 10.1038/nmat2403). The group used scanning tunneling microscopy, reflection absorption infrared spectroscopy, and density functional theory (DFT) to study the formation of water chains on copper. They found that the chains form from water molecules arranged into face-sharing pentagons. DFT computations indicate that the water pentagons are favored over hexagons on copper surfaces because the pentagons maximize the proportion of oxygen atoms that interact with the copper while maintaining a strong hydrogen-bonding network between the water molecules. More experiments are needed to identify the detailed arrangements of water molecules at interfaces, the authors say. "Future studies should focus on identifying structures that optimize the balance between water-metal and water-water bonding, rather than concentrating overly on hexagonal packing arrangements," the authors write.
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