窄碳纳米管中的强关联和Fickian水扩散
Strong Correlations and Fickian Water Diffusion in Narrow Carbon Nanotubes
摘要：
我们已经使用原子分子动力学（MD）模拟研究的结构和动力学的水分子内的开放式碳纳米管放置在一个浴的水分子。纳米管的大小只允许水分子在纳米管内排成一列。纳米管内部的水分子在室温下表现出类似固体的有序性，我们通过计算对关联函数来量化。它示出，即使对于最长的观察时间，纳米管内的水分子的扩散模式是Fickian的，而不是亚扩散。我们还提出了一个一维的无规行走模型的水分子内的纳米管的扩散。我们发现从随机游走模型和MD模拟计算的均方位移之间的良好协议，从而确认水分子在纳米管内进行正常模式扩散。我们将这种行为归因于强烈的位置相关性，导致纳米管内的所有水分子作为单个物体集体移动。水分子在纳米管内的平均停留时间与纳米管长度成二次方关系。
英文摘要：
We have used atomistic molecular dynamics (MD) simulations to study the structure and dynamics of water molecules inside an open ended carbon nanotube placed in a bath of water molecules. The size of the nanotube allows only a single file of water molecules inside the nanotube. The water molecules inside the nanotube show solid-like ordering at room temperature, which we quantify by calculating the pair correlation function. It is shown that even for the longest observation times, the mode of diffusion of the water molecules inside the nanotube is Fickian and not sub-diffusive. We also propose a one-dimensional random walk model for the diffusion of the water molecules inside the nanotube. We find good agreement between the mean-square displacements calculated from the random walk model and from MD simulations, thereby confirming that the water molecules undergo normal-mode diffusion inside the nanotube. We attribute this behavior to strong positional correlations that cause all the water molecules inside the nanotube to move collectively as a single object. The average residence time of the water molecules inside the nanotube is shown to scale quadratically with the nanotube length.
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