Molecular dynamics simulation of friction and energy dissipation between carbon nanotube and graphite substrate

Friction and energy dissipation in commensurate and incommensurate contacts between SWCNT (10,10) and graphite substrate were investigated using molecular dynamics simulations. The SWCNT (10,10) was first relaxed to the equilibrium state, then a force was applied along the lateral direction for a period of time to set the nanotube into motion. After the applied force being removed, the carbon nanotube moved in relative to the substrate in decelerating speed until it came to rest. In commensuration case, firstly carbon nanotube slides on graphite, then switches between sliding and rolling due to the periodic change of atomic configuration during the motion. Lateral force on carbon nanotube also revealed periodic nature during sliding period. In incommensurate case, SWCNT (10,10) slided on graphite during the whole process, and lateral force was opposite to the motion. The study on a pair of interacting atoms in relative motion indicates that approach-separation in vertical direction between atoms of carbon nanotube and graphite leads to a broken of symmetry in lateral force, which may relate to the origin of friction. In commensurate and incommensurate case, interacting forces between carbon nanotube and graphite are both repulsive, and atomic collisions resulted in energy dissipation in the cases under study. Friction-velocity curves of SWCNT (10,10) show linear distribution, which confirms that viscous dissipation dominanted the dynamics process.