In this work, we demonstrate the dynamic equivalence between the members of the family of Brownian fluids whose particles interact through strongly repulsive radially symmetric soft-core potentials. We specifically consider pair potentials proportional to inverse powers of $(r/\sigma ).\mathrm{}$ This equivalence is the dynamic extension of the static equivalence between all these pair potentials and the hard-sphere fluid, assumed in the treatment of soft-core reference potentials in the classical (Weeks-Chandler-Andersen or Barker-Henderson) perturbation theories of simple liquids. In contrast with the strict hard-sphere Brownian system, in the case of soft-sphere potentials the conventional Brownian dynamics algorithm is indeed well defined. We find that, except for small values of $\nu ,$ and/or very short times, the dynamic properties of all these systems collapse into a single universal curve, upon a well-defined rescaling of the time and distance variables. This family of systems includes the hard-sphere limit. This observation permits a conceptually simple, new, and accurate Brownian dynamics algorithm to simulate the dynamic properties of the hard-sphere model dispersion without hydrodynamic interactions. Such an algorithm consists of the straightforward rescaling of the Brownian-dynamics simulated properties of any of the dynamically equivalent soft-sphere systems.

• Received 18 December 2002

DOI:https://doi.org/10.1103/PhysRevE.68.011405