Department of Physics, Indian Institute of Science, Bangalore 560 012, India.
ACS Nano. 2010 Feb 23;4(2):985-91. doi: 10.1021/nn900858a.
We use atomistic molecular dynamics (MD) simulations to study the diffusion of water molecules confined inside narrow (6,6) carbon nanorings. The water molecules form two oppositely polarized chains. It is shown that the effective interaction between these two chains is repulsive in nature. The computed mean-squared displacement (MSD) clearly shows a scaling with time Deltatheta(2)(t) approximately t(1/2), which is consistent with single-file diffusion (SFD). The time up to which the water molecules undergo SFD is shown to be the lifetime of the water molecules inside these chains. Simulations of "uncharged" water molecules inside the nanoring show the formation of several water chains and yield SFD. These observations conclusively prove that the diffusion is Fickian when there is a single chain of water and SFD is observed only when two or more chains are present.
我们使用原子分子动力学（MD）模拟来研究水分子在狭窄的（6,6）碳纳米环内的扩散。水分子形成了两条极性相反的链。结果表明，这两条链之间的有效相互作用本质上是排斥的。计算得到的均方根位移（MSD）明显显示出与时间的标度关系 Deltatheta(2)(t) 约为 t(1/2)，这与单链扩散（SFD）一致。水分子经历 SFD 的时间被证明是这些链内水分子的寿命。在纳米环内模拟“不带电”的水分子时，会形成几条水分子链并产生 SFD。这些观察结果确凿地证明了，当只有一条水分子链时，扩散是菲克型的，而只有当存在两条或更多条链时，才会观察到 SFD。
