Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Mainz scientists confirm original tetrahedral model of the molecular structure of water

12.02.2013
Resolution of controversy about structure of liquid water

Model of a symmetrical four bond water molecule (oxygen red and hydrogen white)

ill./©: Thomas D. Kühne

Researchers at Johannes Gutenberg University Mainz (JGU) have confirmed the original model of the molecular structure of water and have thus made it possible to resolve a long-standing scientific controversy about the structure of liquid water.

The tetrahedral model was first postulated nearly 100 years ago and it assumes that every water molecule forms a so-called hydrogen bond with four adjacent molecules. This concept was almost toppled in 2004 when an international research group announced that it had experimentally established that water molecules form bonds only with two other molecules.

"The quality of the results was excellent but they merely represent a snapshot of the situation," explained Professor Dr. Thomas Kühne. He has demonstrated the fallacy of the 'double bonding' theory using computer simulations based on new types of combinations of two computational methods recently developed by his group.

Some very special and unique features of water, such as its liquid aggregate state and high boiling point, are attributable to the effect of the hydrogen bonds between the water molecules. The H bonds are formed due to the different charges carried by the oxygen and hydrogen atoms that make up water molecules and the resultant dipolar structure. The traditional, generally accepted view was that water had a tetrahedral structure at room temperature, so that on average each water molecule would be linked with four adjacent molecules via two donor and two acceptor bonds. "In our theoretical approach, the median result we observed over time was always for quadruple bonding," said Kühne. Thanks to the new simulations, he and his colleague Dr. Rhustam Khaliullin have now been able to confirm the old model and also supply an explanation for why double bonding was observed in 2004. According to Kühne, the result was not indicative of double bonding "but of instantaneous asymmetrical fluctuation" only.

There is thus significant asymmetry in the four H bonds of the tetrahedral model because of the different energy of the contacts. This asymmetry is the result of temporary disruptions to the hydrogen bond network, which take the form of extremely short term fluctuations occurring on a timescale of 100 to 200 femtoseconds. These fluctuations mean that one of the two donor or acceptor bonds is temporarily much stronger than the other. But these fluctuations precisely cancel each other out so that, on average over time, the tetrahedral structure is retained.

The results reported in 2004 using x-ray absorption spectroscopy were obtained using water molecules with high levels of momentary asymmetry, which is why essentially only two strong hydrogen bonds were observed in an otherwise tetrahedral structure. "Our findings have important implications as they help reconcile the symmetric and asymmetric views on the structure of water," write the scientists in an article published in Nature Communications. The results may also be relevant to research into molecular and biological systems in aqueous solutions and provide insight into protein folding, for example.

The work of Thomas Kühne's group was undertaken within an interdisciplinary joint project and was funded by the Research Unit Center for Computational Sciences at Johannes Gutenberg University Mainz.

Publication:
Thomas D. Kühne, Rustam Z. Khaliullin
Electronic signature of the instantaneous asymmetry in the first coordination shell of liquid water
Nature Communications, February 2013
doi:10.1038/ncomms2459
http://www.nature.com/ncomms/journal/v4/n2/full/ncomms2459.html

Further information:
Junior Professor Dr. Thomas D. Kühne
Institute of Physical Chemistry
Research Unit Center for Computational Sciences
Johannes Gutenberg University Mainz
D 55099 Mainz, GERMANY
phone +49 6131 39-23699
e-mail: kuehne@uni-mainz.de
http://www.tc.uni-mainz.de/index-Dateien/Page376.html
http://www.csm.uni-mainz.de/eng/242.php

Petra Giegerich | idw
Further information:
http://www.uni-mainz.de/presse/16217_ENG_HTML.php
http://www.nature.com/ncomms/journal/v4/n2/full/ncomms2459.html
http://www.csm.uni-mainz.de/eng/242.php

More articles from Life Sciences:

nachricht The malaria pathogen’s cellular skeleton under a super-microscope
18.04.2014 | Helmholtz-Zentrum für Infektionsforschung

nachricht Synapses – stability in transformation
17.04.2014 | Max Planck Institute of Neurobiology, Martinsried

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Anzeige

Anzeige

Event News

Siemens at the 2014 UIC ERTMS World Conference in Istanbul

01.04.2014 | Event News

AERA Meeting: German and US-American educational researchers in dialogue

28.03.2014 | Event News

WHS Regional Meeting: International experts address health challenges in Latin America

24.03.2014 | Event News

 
Latest News

A cross-section of the Universe

18.04.2014 | Physics and Astronomy

More, bigger wildfires burning western U.S., study shows

18.04.2014 | Studies and Analyses

High disease load reduces mortality of children

18.04.2014 | Social Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>