A molecular-dynamics simulation is carried out for particles (tracers) interacting with a screened Coulomb potential in three dimensions. A phase transition is observed from a liquid to an fcc solid on reducing the temperature at a fixed density, consistent with previous studies. In the liquid phase, the variation of the rms displacement ${\mathit{R}}_{\mathrm{tr}}$ of the charged particles with time seems to depend on the density and the temperature. In the short-time regime, the effective exponent k for the subdiffusive power-law behavior, i.e., ${\mathit{R}}_{\mathrm{tr}}$∼${\mathit{t}}^{\mathit{k}}$, decreases on increasing the density and lowering the temperature. A crossover from subdiffusive to a diffusive behavior is observed for a wide density regime in the liquid phase. At high temperatures and large densities, a single power law does not seem to describe the variation of ${\mathit{R}}_{\mathrm{tr}}$ with t.

• Received 3 February 1993

DOI:https://doi.org/10.1103/PhysRevE.47.3246