Very low friction state of a dodecane film confined between mica surfaces.

The existence of a very low friction state of a lubrication film is demonstrated in nonequilibrium molecular dynamics simulations of a six-layer dodecane film between mica walls. We argue that this low friction state is thermodynamically stable with respect to the well documented high friction film, the latter being a metastable state. These results are in striking accord with the recent report of Zhu and Granick [Phys. Rev. Lett. 93, 096101 (2004).]. The extreme low friction is the result, not of wall slip, but of layer sliding throughout the film, a mechanism similar to solid lubrication.