  Recent nanofriction experiments of xenon on graphene revealed that the slip
onset can be induced by increasing the adsorbate coverage above a critical
value, which depends on temperature. Moreover, the xenon slippage on gold is
much higher than on graphene in spite of the same physical nature of the
interactions. To shed light on these intriguing results we have performed
molecular dynamics simulations relying on ab initio derived potentials. By
monitoring the interfacial structure factor as a function of coverage and
temperature, we show that the key mechanism to interpret the observed
frictional phenomena is the size-dependence of the island commensurability. The
latter quantity is deeply affected also by the lattice misfit, which explains
the different frictional behavior of Xe on graphene and gold.
