8 research outputs found
Dynamical transitions in correlated driven diffusion in a periodic potential
The diffusion of a two-dimensional array of particles driven by a constant
force in the presence of a periodic external potential exhibits a hierarchy of
dynamical phase transitions when the driving force is varied. This behavior can
be explained by a simple phenomenological approach which reduces the system of
strongly interacting particles to weakly interacting quasi-particles (kinks).
The richness of the strongly coupled system is however not lost because,
contrary to a single-Brownian particle, the array shows an hysteretic behavior
even at non-zero temperature. The present investigation can be viewed as a
first step toward understanding nanotribology.Comment: 4 pages, 3 pictures, revtex to appear in Phys Rev. Let
Boundary lubrication properties of materials with expansive freezing
We have performed molecular dynamics simulations of solid-solid contacts
lubricated by a model fluid displaying many of the properties of water,
particularly its expansive freezing. Near the region where expansive freezing
occurs, the lubricating film remains fluid, and the friction force decreases
linearly as the shear velocity is reduced. No sign of stick-slip motion is
observed even at the lowest velocities. We give a simple interpretation of
these results, and suggest that in general good boundary lubrication properties
will be found in the family of materials with expansive freezing.Comment: Version to appear in Phys. Rev. Let