Velocity-dependent threshold behavior of wearless nano-friction

A law of friction accompanying steady sliding motion between crystal lattices constituting a nano-electromechanical system (NEMS) was revealed by molecular dynamics simulations using simplified models. A threshold phenomenon was predicted as a common feature characterizing dependence of the wearless frictional resistance on the sliding velocity vstroke. The threshold sliding velocity vth linearly depends on the lattice-constant ratio, which was turned out to be a key parameter determining vth. The increased dynamic-frictional force in the case of vstroke > vth possibly reflects enhanced rate of energy dissipation via anharmonicity of the interatomic potential due to resonant excitation of phase-matched normal phonon modes in the crystal lattices sliding relative to each other.