Hu Haibao, Bao Luyao, Priezjev Nikolai V, Luo Kai
School of Marine Science and Technology, Northwestern Polytechnical University, Xi'an, Shaanxi 710072, People's Republic of China.
Department of Mechanical and Materials Engineering, Wright State University, Dayton, Ohio 45435, USA.
J Chem Phys. 2017 Jan 21;146(3):034701. doi: 10.1063/1.4973640.
The slip behavior of simple fluids over atomically smooth surfaces was investigated in a wide range of wall-fluid interaction (WFI) energies at low shear rates using non-equilibrium molecular dynamics simulations. The relationship between slip and WFI shows two regimes (the strong-WFI and weak-WFI regimes): as WFI decreases, the slip length increases in the strong-WFI regime and decreases in the weak-WFI regime. The critical value of WFI energy that separates these regimes increases with temperature, but it remains unaffected by the driving force. The mechanism of slip was analyzed by examining the density-weighted average energy barrier (ΔE¯) encountered by fluid atoms in the first fluid layer (FFL) during their hopping between minima of the surface potential. We demonstrated that the relationship between slip and WFI can be rationalized by considering the effect of the fluid density distribution in the FFL on ΔE¯ as a function of the WFI energy. Moreover, the dependence of the slip length on WFI and temperature is well correlated with the exponential factor exp(-ΔE¯/(kT)), which also determines the critical value of WFI between the strong-WFI and weak-WFI regimes.
利用非平衡分子动力学模拟，在低剪切速率下的广泛壁 - 流体相互作用（WFI）能量范围内，研究了简单流体在原子级光滑表面上的滑移行为。滑移与WFI之间的关系呈现出两种状态（强WFI状态和弱WFI状态）：随着WFI降低，在强WFI状态下滑移长度增加，而在弱WFI状态下滑移长度减小。分隔这些状态的WFI能量临界值随温度升高，但不受驱动力影响。通过检查第一流体层（FFL）中的流体原子在表面势阱之间跳跃时遇到的密度加权平均能垒（ΔE¯），分析了滑移机制。我们证明，通过考虑FFL中流体密度分布对作为WFI能量函数的ΔE¯的影响，可以解释滑移与WFI之间的关系。此外，滑移长度对WFI和温度的依赖性与指数因子exp(-ΔE¯/(kT))密切相关，该指数因子也决定了强WFI和弱WFI状态之间的WFI临界值。
