Molecular dynamics study of interfacial slip behavior of ultrathin lubricating films

Rheology and slip properties of ultrathin lubricating films were studied using molecular dynamics simulation. The model system consisted of two solid walls and of the lubricant molecules confined between the walls. N-decane was chosen to model the lubricant molecules. The results show that the particle density in the films periodically oscillates indicating a formation of layered structures. The simulation also shows that the averaged velocities of the molecules are largely distributed linearly, with a slip velocity at the solid-liquid interface. The slip ratio on the walls increases as the shear rate increases and the increase is significant for very high shear rates. Another important phenomenon is that the wall slip may appear at low shear rates in molecularly thin films. A solidification process progresses in the thin films and the slip ratio of the low shear rate may be considered as a convenient criterion to measure this solidification in the lubricating films.