Application of rigid-body dynamics and semiclassical mechanics to molecular bearings

Various types of molecular bearings, gears, joints, etc have recently been proposed and studied in the growing nanotechnology literature using classical molecular dynamics. In a previous study, we reported simulations for several model graphite bearings using fully atomistic molecular dynamics simulations. It was subsequently found that various predictions based on simulations of this type do not agree with those of a more correct quantum approach owing to leakage of the quantum zero-point vibrational energy in the molecular dynamics simulations. In this study we use the tools of rigid-body dynamics to address the zero-point energy problem. The results of these simulations are striking in the sense that under certain conditions the bearing is found to be frictionless, as previously alluded to by Feynman. A frictionless bearing will undergo `superrotation', a classical dynamical behavior reminiscent of superfluidity. States which are chaotic in nature may not have this new characteristic, an issue we investigate with maps of phase space.