First-Principle Molecular Dynamics of Sliding Diamond Surfaces: Tribochemical Reactions with Water and Load Effects

Ab initio molecular dynamics offers an unexpected tool to understand many aspects of complex and macroscopic phenomena, like friction, lubrication, and surface passivation through chemical reactions induced by load and confinement, as found in recent works (Zilibotti et al., in Phys. Rev. Lett. 111:146101, 2013; De Barros Bouchet et al., J Phys Chem C 116:6966, 2012). Here we review the results of first-principle molecular dynamics simulations of diamond interfaces interacting with water molecules, at different concentrations. We found that the molecular confinement induced by the applied load promotes water dissociation. The consequent surface passivation prevents the formation of carbon bonds across the interface, reducing adhesion and friction. The possibility to extend the use of an atomistic approach to understand the kinetics of tribochemical reactions and their effects on friction will also be discussed.