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.
ACS Nano. 2015 Oct 27;9(10):9877-84. doi: 10.1021/acsnano.5b04947. Epub 2015 Sep 21.
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.
利用分子动力学模拟研究了非均匀纳米受限下水的相行为及其相关相变。通过一个平底和一个凸顶构建了纳米受限环境。在 300 K 下，受限水可以看作是单层、双层和三层液相共存，以适应非均匀受限环境。随着液相密度的增加，具有不均匀层的受限水分别转变成二维冰晶，层数不变，氧原子呈菱形面内对称。单层水首先经历向弯曲冰纳米带的转变，然后双层水转变为菱形冰纳米带，接着是三层水向三层冰纳米带的转变。在低液相密度下，通过逐渐降低温度也可以实现非均匀受限内的顺序局部液相到固相的转变。这些在非均匀纳米受限下水的相行为的发现不仅扩展了受限水的相图，而且对实际的纳米流控系统和微孔材料也有意义。
