  The motion of a cylindrical crystalline nanoparticle sandwiched between two
crystalline planes, one stationary and the other pulled at a constant velocity
and pressed down by a normal load, is considered theoretically using a planar
model. The results of our model calculations show that, depending on load and
velocity, the nanoparticle can be either rolling or sliding. At sufficiently
high normal loads, several sliding states characterized by different friction
forces can coexist, corresponding to different orientations of the
nanoparticle, and allowing one to have low or high friction at the same pulling
velocity and normal load.
