Molecular Dynamics of Surface-Moving Thermally Driven Nanocars.

We developed molecular models describing the thermally initiated motion of nanocars, nanosized vehicles composed of two to four spherical fullerene wheels chemically coupled to a planar chassis, on a metal surface. The simulations were aimed at reproducing qualitative features of the experimentally observed migration of nanocars over gold crystals as determined by scanning tunneling microscopy. Coarse-grained-type molecular dynamics simulations were carried out for the species "Trimer" and "Nanotruck", the simplified versions of the experimentally studied nanomachines. Toward this goal, we developed a version of the rigid body molecular dynamics based on the symplectic quaternion scheme in conjunction with the Nose-Poincare thermostat approach. Interactions between rigid fragments were described by using the corrected CHARMM force field parameters, while several empirical models were introduced for interactions of nanocars with gold crystals. With the single adjusted potential parameter, the computed trajectories are consistent with the qualitative features of the thermally activated migration of the nanocars: the primary pivoting motion of Trimer and the two-dimensional combination of translations and pivoting of Nanotruck. This work presents a first attempt at a theoretical analysis of nanocars' dynamics on a surface by providing a computationally minimalist approach.