The weird world of ultra-confined water

We tend to think we know a lot about the different forms of H₂O; ice, water and steam are all materials that we encounter in our daily lives. However, scientists at Oakridge National Laboratories in the US claim to have found a new state of water in “highly confined” environments in Beryl, a mineral.

The Beryl mineral was found to have channels about 5×10^-10m wide (this is on the scale of single atoms) in which the molecule H₂O was confined. To find these channels the scientists used a technique called “neutron diffraction” whereby neutrons of high energy collide with the material and their interactions with the material gives clues to the structure and composition.

In these channels the researchers claim that water molecules exhibit quantum tunnelling behaviour. Quantum tunnelling is where particles cross barriers that according to classical physics they should not be able to cross. In the case of these water molecules, it appears that the oxygen and hydrogen atoms in the molecule are delocalised, occupying six symmetrically equivalent positions simultaneously.

This is interesting enough but it was also found through neutron diffraction experiments that the average kinetic energy of the protons in the molecules have a far lower kinetic energy than would be expected in bulk water.

These findings lead to questions that concern many aspects of science. In biology, cell membranes have environments in ion exchange systems where this state of water may be present. In materials science, it will be relevant to consider how water may behave in carbon nanotubes or along grain boundaries in metals. And even without application this research is fascinating, as Dr Lawrence Anovitz remarks, “this discovery represents a new fundamental understanding of the behaviour of water and the way water utilizes energy”.

Image credit: Jeff Scovil

https://www.ornl.gov/news/ornl-researchers-discover-new-state-water-molecule