Test of the Stokes-Einstein Relation in a Two-Dimensional Yukawa Liquid

The Stokes-Einstein relation, relating the diffusion and viscosity coefficients D and η, is tested in two dimensions. An equilibrium molecular-dynamics simulation was used with a Yukawa pair potential. Regimes are identified where motion is diffusive and D is meaningful. The Stokes-Einstein relation, Dη∝kBT, was found to be violated near the disordering transition; under these conditions collective particle motion exhibits dynamical heterogeneity. At slightly higher temperatures, however, the Stokes-Einstein relation is valid. These results may be testable in strongly coupled dusty plasma experiments