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Fast Rotational Diffusion of Water Molecules in a 2D Hydrogen Bond Network at Cryogenic Temperatures



Timothy R Prisk, C. Hoffmann, A. I. Kolesnikov, E. Mamontov, A. A. Podlesnyak, X. Wang, P. R. C. Kent, L. M. Anovitz


Individual water molecules or small clusters of water molecules contained within microporous minerals present an extreme case of confinement where the local structure of hydrogen bond networks are dramatically altered from bulk water phases. In the zinc silicate hemimorphite, for example, the water molecules form a two-dimensional hydrogen bond network with hydroxyl groups on the crystal framework. Here, we present a combined experimental and theoretical study of the structure and dynamics of water molecules within this network. We find that the water molecules undergo a continuous phase transition in their orientational configuration in a manner analogous to a two-dimensional Ising model. The incoherent dynamic structure factor reveals two thermally activated relaxation processes, as faster one on a subpicosecond time scale and a slower one on a 10-100 ps time scale, at temperatures between 70-130 K. The slow process is an in-plane reorientation of the water molecule involving the breaking of hydrogen bonds with the framework that, despite the low temperatures involved, is analogous to the rotational diffusion of water molecules in the bulk liquid. The fast process is a localized motion of the water molecule that has no apparent analogs within bulk or confined phases of water.
Physical Review Letters


, T. , Hoffmann, C. , , A. , Mamontov, E. , , A. , Wang, X. , C., P. and , L. (2018), Fast Rotational Diffusion of Water Molecules in a 2D Hydrogen Bond Network at Cryogenic Temperatures, Physical Review Letters, [online], (Accessed April 19, 2024)
Created May 9, 2018, Updated August 27, 2018