Using computational modeling and neutron scattering, physicists have discovered a novel state of water molecule.
Physicists discovered that water in the mineral beryl displays some unique and unexpected characteristics. Image credit: Jeff Scovil.
In a paper published in the journal Physical Review Letters, the scientists describe a new ‘quantum tunneling state’ of water molecules confined in hexagonal ultra-small channels – 5 angstrom across – of the mineral beryl, characterized by extended proton and electron delocalization.
“At low temperatures, this tunneling water exhibits quantum motion through the separating potential walls, which is forbidden in the classical world,” said Dr. Alexander Kolesnikov of Oak Ridge National Laboratory, lead author on the paper.
“This means that the oxygen and hydrogen atoms of the water molecule are ‘delocalized’ and therefore simultaneously present in all six symmetrically equivalent positions in the channel at the same time. It’s one of those phenomena that only occur in quantum mechanics and has no parallel in our everyday experience.”
The existence of the tunneling state of water should help physicists better describe the thermodynamic properties and behavior of water in highly confined environments such as water diffusion and transport in the channels of cell membranes, in carbon nanotubes and along grain boundaries and at mineral interfaces in a host of geological environments.
“The discovery is apt to spark discussions among materials, biological, geological and computational scientists as they attempt to explain the mechanism behind this phenomenon and understand how it applies to their materials,” said co-author Dr. Lawrence Anovitz, also from Oak Ridge National Laboratory.
“This discovery represents a new fundamental understanding of the behavior of water and the way water utilizes energy,” he added.
“It’s also interesting to think that those water molecules in your aquamarine or emerald ring – blue and green varieties of beryl – are undergoing the same quantum tunneling we’ve seen in our experiments.”
The neutron scattering and computational chemistry experiments showed that, in the tunneling state, the water molecules are delocalized around a ring so the water molecule assumes an unusual double top-like shape.
“The average kinetic energy of the water protons directly obtained from the neutron experiment is a measure of their motion at almost absolute zero temperature and is about 30% less than it is in bulk liquid or solid water,” Dr. Kolesnikov said.
“This is in complete disagreement with accepted models based on the energies of its vibrational modes.”
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Alexander I. Kolesnikov et al. 2016. Quantum Tunneling of Water in Beryl: A New State of the Water Molecule. Phys. Rev. Lett., vol. 116, no. 16; doi: 10.1103/PhysRevLett.116.167802
