It's raining pentagons

March 8, 2009
A computer generated image of a pentamer ice chain (red and white) on a plane surface (brown). Credit: LCN

This week's Nature Materials (09 March 2009) reveals how an international team of scientists led by researchers at the London Centre for Nanotechnology (LCN) at UCL have discovered a novel one dimensional ice chain structure built from pentagons that may prove to be a step toward the development of new materials which can be used to seed clouds and cause rain.

Although the 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 and not hexagons" says Dr Michaelides.

"This discovery leads to fundamental new understanding about the nature of hydrogen bonding at interfaces (there is no a priori rule that hexagons should form) 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."

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 Dr Angelos 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.

"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," explains the paper's first author Dr 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."

The formation of nanoscale ice crystals (i.e. nucleation) plays a key role in fields as diverse as atmospheric chemistry and biology. Ice nucleation on metal surfaces affords an opportunity to watch this process unfold at the molecular-scale on a well defined, plane interface. A common feature of structural models for such films of ice is that they are built from hexagonal arrangements of molecules.

In order to address the challenge of characterising ice on the nanoscale, the team from the LCN joined up with a team of experimentalists from the University of Liverpool (lead by Professor Andrew Hodgson) to examine ice formation on a very well defined, atomically flat copper surface. The Liverpool group performed scanning tunneling microscopy experiments and the LCN and Berlin teams carried out ab initio calculations to predict what the microscopy results would be. Only through the combination of these two state-of-the-art approaches were they able to definitively show that the ice structures that form are made from pentagons.

Source: University College London

Explore further: What flows on Pluto?

Related Stories

What flows on Pluto?

August 20, 2015

It's now been over a month since the New Horizons spacecraft flew by one of the last unknown outposts of our solar system and although we've only just seen a trickle of the data it collected, it has all been rather exciting. ...

The Planet Saturn

August 3, 2015

The farthest planet from the Sun that be observed with the naked eye, the existence of Saturn has been known for thousands of years. And much like all celestial bodies that can be observed with the aid of instruments – ...

Study calculates the speed of ice formation

August 3, 2015

Researchers at Princeton University have for the first time directly calculated the rate at which water crystallizes into ice in a realistic computer model of water molecules. The simulations, which were carried out on supercomputers, ...

Macroscopic quantum phenomena discovered in ice

July 21, 2015

(Phys.org)—Scientists have discovered an anomaly in the properties of ice at very cold temperatures near 20 K, which they believe can be explained by the quantum tunneling of multiple protons simultaneously. The finding ...

How frogs and fish can help us learn to freeze humans

June 3, 2015

From Star Wars to Futurama to Alien, the idea that humans can be frozen in time in order to be awoken later is a well-established sci-fi trope. While stopping biological time or inducing long-term hibernation is still as ...

Recommended for you

Electrical circuit made of gel can repair itself

August 25, 2015

(Phys.org)—Scientists have fabricated a flexible electrical circuit that, when cut into two pieces, can repair itself and fully restore its original conductivity. The circuit is made of a new gel that possesses a combination ...

Scientists grow high-quality graphene from tea tree extract

August 21, 2015

(Phys.org)—Graphene has been grown from materials as diverse as plastic, cockroaches, Girl Scout cookies, and dog feces, and can theoretically be grown from any carbon source. However, scientists are still looking for a ...

2 comments

Adjust slider to filter visible comments by rank

Display comments: newest first

LariAnn
not rated yet Mar 09, 2009
Interesting - if water molecules can arrange in pentagons as well as hexagons, then perhaps, under the proper conditions, they can be arranged in a form like unto a geodesic dome, which consists of hexagons and pentagons. What intriguing properties might such a water structure have?
Alizee
Apr 11, 2009
This comment has been removed by a moderator.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.