  We present Molecular Dynamics simulations of one- and two-dimensional
bead-spring models sliding on incommensurate substrates. We investigate how
sliding friction is affected by interaction anharmonicity and structural
defects. In their absence, we confirm earlier findings, namely, that at special
resonance sliding velocities, friction is maximal. When sliding off-resonance,
partially thermalized states are possible, whereby only a small number of
vibrational modes becomes excited, but whose kinetic energies are already
Maxwell-Boltzmann distributed. Anharmonicity and defects typically destroy
partial thermalization, and instead lead to full thermalization, implying much
higher friction. For sliders with periodic boundaries, thermalization begins
with vibrational modes whose spatial modulation is compatible with the
incommensurate lattice. For a disc-shaped slider, modes corresponding to
modulations compatible with the slider radius are initially the most dominant.
By tuning the mechanical properties of the slider's edge, this effect can be
controlled, resulting in significant changes in the sliding distance covered.
