Institute for Problems of Mechanical Engineering, Russian Academy of Sciences, 199178, Bolshoi 61, V. O., St. Petersburg, Russia.
Phys Rev E. 2019 Aug;100(2-1):023106. doi: 10.1103/PhysRevE.100.023106.
Molecular dynamics simulations of equilibrium structures and flows of nonpolar argon atoms confined by single-walled carbon nanotubes (SWCNTs) with circular cross section and rectangular cross section having the same area and the ratio between its sides 1:4 have been performed. It has been shown that, inside these SWCNTs, argon atoms form the spatially ordered structures and, under action of external driving forces they move collectively along SWCNT's axes. It has been also obtained that there are two regimes of such collective movement. In the first regime, when the driving external force f_{x0} is lower than a certain critical value f_{xc}, argon atoms flow through these SWCNTs with the finite average flow velocity. In the second regime, when the driving external force f_{x0} exceeds f_{xc}, the retarding friction force acting on argon atoms from bounding wall carbon atoms gradually drops to zero and the average flow velocity exhibits an unlimited growth. Moreover, when the retarding friction force becomes close to zero, the fluid will continue to flow with the same constant velocity at switched off external driving force. Hence, in the second regime, argon atoms inside the above-mentioned SWCNTs demonstrate the ballistic frictionless flows which resemble the superfluidic liquid flow. It has been shown that collective frictionless ballistic flows of argon atoms through SWCNTs are caused by the crystalline structure of SWCNT's bounding walls and, for the same SWCNTs with random distribution of carbon atoms on the bounding walls, one can observe only the first regime of the argon atom flows.
采用分子动力学方法模拟了具有圆形和矩形横截面（面积相同，纵横比为 1:4）的单壁碳纳米管（SWCNT）中平衡结构和非极性氩原子流动。结果表明，在这些 SWCNT 中，氩原子形成了空间有序结构，在外部驱动力的作用下，它们沿着 SWCNT 的轴集体移动。还发现，这种集体运动存在两种模式。在第一种模式下，当外部驱动力 f_{x0}低于某个临界值 f_{xc}时，氩原子以有限的平均流速流过这些 SWCNT。在第二种模式下，当外部驱动力 f_{x0}超过 f_{xc}时，来自边界碳原子的阻碍摩擦力逐渐降至零，平均流速呈无限增长。此外，当阻碍摩擦力接近零时，即使关闭外部驱动力，流体也将以相同的恒定速度继续流动。因此，在第二种模式下，上述 SWCNT 内的氩原子表现出类似超流液体流动的无阻力弹道流动。结果表明，SWCNT 边界壁的晶体结构导致了氩原子通过 SWCNT 的集体无阻力弹道流动，而对于边界壁上碳原子随机分布的相同 SWCNT，只能观察到氩原子流动的第一种模式。
