  We present a computational study of sliding between gold clusters and a
highly oriented pyrolytic graphite substrate, a material system that exhibits
ultra-low friction due to structural lubricity. By means of molecular dynamics,
it is found that clusters may undergo spontaneous rotations during manipulation
as a result of elastic instability, leading to attenuated friction due to
enhanced interfacial incommensurability. In the case of a free cluster, shear
stresses exhibit a non-monotonic dependency on the strength of the tip-cluster
interaction, whereby rigid clusters experience nearly constant shear stresses.
Finally, it is shown that the suppression of the translational degrees of
freedom of a cluster's outermost-layer can partially annihilate out-of-plane
phonon vibrations, which leads to a reduction of energy dissipation that is in
compliance with Stokesian damping. It is projected that the physical insight
attained by the study presented here will result in enhanced control and
interpretation of manipulation experiments at structurally lubric contacts.
