Orientations of special water dipoles that accelerate water molecules exiting from carbon nanotube

One-dimensional ordered water molecules entering and exiting from a carbon nanotube with an appropriate radius are studied with molecular dynamics simulations.It can be found that a water molecule near the nanotube end is more likely to be expelled from the nanotube if its dipole is almost perpendicular to the nanotube axis.The key to this observation is that those water molecules axe closer to the wall of the nanotube away from the equilibrium position of the Lennar-Jones (LJ) potential.Thus,the interaction energy for those water molecules is relatively high.There are two particular structures of the perpendicular water molecule depending on the dipole direction of the adjacent water molecule in the nanotube.Although the probabilities of these structures are quite small,their contributions to the net flux across the nanotube end are approximately equal to the predominant structures.The present findings further show the possibility of controlling the water flow by regulating the dipole directions of the water molecules inside the nanochannels.     

Orientations of special water dipoles that accelerate water molecules exiting from carbon nanotube

One-dimensional ordered water molecules entering and exiting from a carbon nanotube with an appropriate radius are studied with molecular dynamics simulations. It can be found that a water molecule near the nanotube end is more likely to be expelled from the nanotube if its dipole is almost perpendicular to the nanotube axis. The key to this observation is that those water molecules are closer to the wall of the nanotube away from the equilibrium position of the Lennar-Jones (LJ) potential. Thus, the interaction energy for those water molecules is relatively high. There are two particular structures of the perpendicular water molecule depending on the dipole direction of the adjacent water molecule in the nanotube. Although the probabilities of these structures are quite small, their contributions to the net flux across the nanotube end are approximately equal to the predominant structures. The present findings further show the possibility of controlling the water flow by regulating the dipole directions of the water molecules inside the nanochannels.     

提高水分子流出纳米碳管速度的特殊水分子偶极排布研究

使用分子动力学的方法,研究了水分子进出狭窄碳纳米管的过程．发现管口处水分子的偶极垂直于碳管时容易流出碳管．根据碳管中与之相邻的水分子的偶极方向可以把这种特殊构型分为2类．虽然,这2类特殊结构的出现概率非常小,但是它们对净流过碳管水分子的贡献与其它结构的贡献基本相同．这2种偶极排布中水分子比较接近管壁、远离Lennard-Jones势的平衡位置,导致这2种偶极排布中水分子能量升高,处于相对不稳定的状态,容易流出碳管．这个发现表明可以通过调控碳纳米管内的水分偶极方向控制管内的水分子流动．