Atomic alignment and friction behavior of dense fullerene packings revealed by molecular dynamics simulations

Recent experimental and simulation work explores the possibility of scaling up the microscopic phenomenon of superlubricity to the macroscopic scale. Here, we investigate the lubrication behavior of dense packings of C₆₀ fullerenes sandwiched between two rigid fullerene slabs using atomistic simulations. Using a range of atomic potentials common for carbon-based nanomaterials, we investigate the fullerenes’ atomic stacking and resulting friction properties of the packing as a function of boundary roughness and applied normal load. We find superlubric behavior for flat boundaries due to boundary slip, but finite friction for rough boundaries, due to bulk shear and the related energy dissipation in the bulk. The atomistic simulations reveal a preferred AA-type atomic stacking, which changes to TA-type stacking as the applied load is increased. This is accompanied by a loss of rolling motion of the particles in the highly condensed sheared packing. These results provide atomistic insight into the collective interactions of superlubric particles that exhibit many rotational and translational degrees of freedom in dense packings, and reveal their emergent frictional properties for friction-reduction applications.