Volume 90 Issue 21 | p. 33 | Concentrates
Issue Date: May 21, 2012

Winning Water Cluster Structure

A cage-shaped isomer is the lowest energy structure for hexameric water clusters
Department: Science & Technology
News Channels: Analytical SCENE
Keywords: water, water structure, microwave spectroscopy, rotational spectrum
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The cage isomer is lower in energy than the prism and book isomers.
Credit: Science
Structures of three hexameric water clusters as measured with microwave rotational spectroscopy. The cage is the lowest energy structure. Lines indicate hydrogen bonds.
 
The cage isomer is lower in energy than the prism and book isomers.
Credit: Science

The lowest energy, and hence most stable, structure for six-molecule water clusters is a “cage,” according to a study in Science (DOI: 10.1126/science.1220574). The hexamer is the smallest water cluster with a three-dimensional hydrogen-bonded network and is key to understanding the structure of liquid water. The cage structure is one of several hexamer clusters that researchers have previously seen. But they have never observed all the differently shaped clusters at the same time. Brooks H. Pate of the University of Virginia; Zbigniew Kisiel of the Polish Academy of Sciences, in Warsaw; George C. Shields of Bucknell University; and coworkers now report observing coexisting “cage,” “prism,” and “book” isomers at low temperatures. The researchers used microwave spectroscopy to measure the rotational spectra of 18O-substituted versions of the clusters and then used the data to construct the clusters’ oxygen framework. They recorded separate spectra using argon, neon, and helium as the carrier gas. When using argon, the researchers observed the cage hexamer but not the others, suggesting that the cage is the lowest energy structure.

 
Chemical & Engineering News
ISSN 0009-2347
Copyright © American Chemical Society

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