Non-Equilibrium Molecular Dynamics Study on Velocity-Dependent Threshold Behavior of Wearless Nano-Friction

In order to develop methods of designing arti…cial materials of desired tribological characteristics for nano-electromechanical systems (NEMS), a better atomistic understanding of wearless-frictional characteristics of mesoscopic solid materials is indispensable. We have searched for laws of wearless friction accompanying steady sliding motion between mesoscopic crystal lattices, by molecular dynamics simulations using simpli…ed twoand threedimensional models [1]. In these studies, several universal features of nanofriction were found such as a simple relationship between the threshold value of the sliding velocity and the lattice-constant ratio. The purpose of the present investigation is to carry out the systematic analyses of the nano-frictional characteristics under steady spatial distribution of the local quasi-temperature [1],[2]. The Nose-Poincare thermostats extended to the non-conservative system were used to maintain a local quasitemperature of the passive particles neighboring the stroking and the …xed layers [1] without drift during a simulation run. By analyzing the dependence of the wearless frictional force on the applied load and the sliding velocity, we elucidated the above-mentioned universal features of nano-friction revealed in our previous studies. Moreover, the spatial distribution of the local pseudo-heat ‡ux was de…ned at the atomic scale and was associated with that of the local quasi-temperature. The results suggested that, unlike the wearless-frictional characteristics of a macroscopic solid system, those of a mesoscopic system re‡ect phonon modes of the lattices sliding relative to each other. Based on these results,