Five-sided ice found, to help seed clouds

March 9th, 2009 - 11:57 am ICT by IANS  

London, March 9 (IANS) The discovery of an ice chain built from pentagons may open the way to developing new materials to seed clouds and cause rain.
Although the six-sided structure of regular ice is well known at the macroscale, its structures are much more mysterious and less well understood at the nanoscale - particularly when ice forms at an interface with matter as is the case in the higher atmosphere on particles of dust.

“For the first time, we have shown that ice can build an extended one dimensional chain structure entirely from pentagons (five-sided structures) and not hexagons (six-sided structures),” said Angelos Michaelides of the London Centre for Nanotechnology (LCN), University College of London (UCL).

“This discovery leads to fundamental new understanding about the nature of hydrogen bonding at interfaces and suggests that when people are searching for new ice nucleating agents which can be used to seed clouds and cause rain, they do not necessarily need to focus on materials that have hexagonal surfaces - other types of surfaces may be good too,” he said.

Ice structures are usually built out of simple hexagonal arrangements of water molecules and this hexagonal building block motif is easily observed in the structures of snowflakes.

However, during their studies Michaelides and co-workers from the Fritz Haber Institute, Berlin, and the University of Liverpool have discovered a natural nanoscale ice structure formed of pentagons, said an UCL release.

“It is important to understand the structure of ice on the nanoscale, and in particular up against solid surfaces because this is how ice crystals form,” explained study co-author Javier Carrasco.

“We need to understand the structure of ice crystals in the upper atmosphere because they play an important role in the formation of clouds and precipitation,” he added.

The study was published in Nature Materials Monday.

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