  Molecular dynamics study of a thin (one to five layers) lubricant film
between two substrates in moving contact are performed using Langevin equations
with an external damping coefficient depending on distance and velocity of
atoms relative the substrates, motivated by microscopic configurations. They
show that the minimal friction coefficient is obtained for the solid-sliding
regime. A detailed analysis of the results, the comparison with other
microscopic modeling approaches of friction, and the evaluation of quantities
that can be compared to experiments, such as the velocity of the transition
from stick-slip to smooth sliding, are used to discuss the relevance of the
microscopic simulations of friction.
