  Molecular dynamic (MD) simulations are applied to investigate the dependency
of the kinetic friction coefficient on the temperature at the nano-scale. The
system is comprised of an aluminum spherical particle consisting of 32000 atoms
in an FCC lattice sliding on a stack of several layers of graphene, and the
simulations have done using LAMMPS. The interaction potential is
charge-optimized many-body (COMB3) potential and a Langevin thermostat keep the
system at a nearly constant temperature. With an assumption of linear viscous
friction, $F_{fr}= - \gamma v$, the kinetic friction coefficient $\gamma$ is
derived and plotted at different temperatures in the interval of $T \in [1,
600] K$. As a result, by increasing temperature, the kinetic friction
coefficient is decreased. Consequently, while the friction is assumed as a
linear viscous model, the results are similar to the thermal activation in
atomic-scale friction. That is, (1) by increasing sliding velocity friction
force will be increased and (2) by increasing temperature, kinetic friction
coefficient decreases.
