Water as a lubricant for graphite: a computer simulation study.

The phase state and shear behavior of water confined between parallel graphite sheets are studied using the grand canonical Monte Carlo technique and TIP4P model for water. In describing the water-graphite interaction, two orientation-dependent potentials are tried. Both potentials are fitted to many-body polarizable model predictions for the binding energy and the equilibrium conformation of the water-graphite complex [K. Karapetian and K. D. Jordan in Water in Confining Geometries, edited by V. Buch and J. P. Devlin (Springer, Berlin, 2003), pp. 139-150]. Based on the simulation results, the property of water to serve as a lubricant between the rubbing surfaces of graphitic particles is associated, first, with the capillary condensation of water occurring in graphitic pores of monolayer width and, second, with the fact that the water monolayer compressed between graphite particles retains a liquidlike structure and offers only slight resistance to shear.