  Simulations of the kinetic friction due to a layer of adsorbed molecules
between two crystalline surfaces are presented. The adsorbed layer naturally
produces friction that is consistent with Amontons' laws and insensitive to
parameters that are not controlled in experiments. The kinetic friction rises
logarithmically with velocity as in many experimental systems. Variations with
potential parameters and temperature follow variations in the static friction.
This correlation is understood through analogy with the Tomlinson model and the
trends are explained with a hard-sphere picture.
