Shape-shifting form of water molecules identified

A multidisciplinary research team has found that a solitary, confined water molecule can exist in a previously unidentified state in which protons and electrons form a delocalized ring around the oxygen atom (Phys. Rev. Lett. 2016, DOI: 10.1103/physrevlett.116.167802). Alexander I. Kolesnikov of Oak Ridge National Laboratory and coworkers used neutron scattering to study water molecules trapped in cavities of the mineral beryl. These crystal lattice cavities are just large enough to fit one water molecule, with no hydrogen bonds to other water molecules or to the beryl cavity atoms. In a classical view, the water molecule sits with the oxygen atom roughly in the center of the cavity and its two hydrogens pointing toward one of the faces, held in place by an ­energy barrier to rotation. Taking a quantum mechanical view, the researchers found that the water molecule can “tunnel” through the barrier and exist in multiple orientations simultaneously. The resulting structure has the centrally located oxygen surrounded by concentric rings of delocalized electrons and protons. The symmetry of this form means that the water molecule has zero electric dipole moment. The team suggests this newfound state of water could also occur in other confined spaces, such as cell membranes.