Water in Inhomogeneous Nanoconfinement: Coexistence of Multilayered Liquid and Transition to Ice Nanoribbons (ACS Nano)

ACS Nano
Water in Inhomogeneous Nanoconfinement: Coexistence of Multilayered Liquid and Transition to Ice Nanoribbons
Hu Qiu, Xiao Cheng Zeng, and Wanlin Guo
DOI: 10.1021/acsnano.5b04947
Key Laboratory for Intelligent Nano Materials and Devices of MOE and State Key Laboratory of Mechanics and Control of Mechanical Structures, Institute of Nano Science, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China
Department of Chemistry and Nebraska Center for Materials and Nanoscience, University of Nebraska−Lincoln, Lincoln, Nebraska 68588, United States
qiuhu@nuaa.edu.cn, xzeng1@unl.edu, wlguo@nuaa.edu.cn.

Abstract
Phase behavior and the associated phase transition of water within inhomogeneous nanoconfinement are investigated using molecular dynamics simulations. The nanoconfinement is constructed by a flat bottom plate and a convex top plate. At 300 K, the confined water can be viewed as a coexistence of monolayer, bilayer, and trilayer liquid domains to accommodate the inhomogeneous confinement. With increasing liquid density, the confined water with uneven layers transforms separately into two-dimensional ice crystals with unchanged layer number and rhombic in-plane symmetry for oxygen atoms. The monolayer water undergoes the transition first into a puckered ice nanoribbon, and the bilayer water transforms into a rhombic ice nanoribbon next, followed by the transition of trilayer water into a trilayer ice nanoribbon. The sequential localized liquid-to-solid transition within the inhomogeneous confinement can also be achieved by gradually decreasing the temperature at low liquid densities. These findings of phase behaviors of water under the inhomogeneous nanoconfinement not only extend the phase diagram of confined water but also have implications for realistic nanofluidic systems and microporous materials.

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