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 Khne. 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 Khne. 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 Khne, the result was not indicative of double bonding "but of instantaneous asymmetrical fluctuation" only.
There is thus significant asymmetry in the fou
|Contact: Junior Professor Dr. Thomas D. Khne|
Johannes Gutenberg Universitaet Mainz