  The pioneer work of Krim and Widom unveiled the origin of the viscous nature
of friction at the atomic scale. This generated extensive experimental and
theoretical activity. However, fundamental questions remain open like the
relation between sliding friction and the topology of the substrate, as well as
the dependence on the temperature of the contact surface. Here we present
results, obtained using molecular dynamics, for the phononic friction
coefficient ($\eta_{ph}$) for a one dimensional model of an adsorbate-substrate
interface. Different commensuration relations between adsorbate and substrate
are investigated as well as the temperature dependence of $\eta_{ph}$. In all
the cases we studied $\eta_{ph}$ depends quadratically on the substrate
corrugation amplitude, but is a non-trivial function of the commensuration
ratio between substrate and adsorbate. The most striking result is a deep and
wide region of small values of $\eta_{ph}$ for substrate-adsorbate
commensuration ratios between $\approx 0.6-0.9$. Our results shed some light on
contradictory results for the relative size of phononic and electronic friction
found in the literature.
