Mapping the glassy dynamics of soft spheres onto hard-sphere behavior
  We show that the dynamics of soft-sphere systems with purely repulsive interactions can be described by introducing an effective hard-sphere diameter determined using the Andersen-Weeks-Chandler approximation. We find that this approximation, known to describe static properties of liquids, also gives a good description of a dynamical quantity, the relaxation time, even in the vicinity of the glass transition. 
Michael Schmiedeberg (1 and 2), Thomas K. Haxton (2), Sidney R. Nagel   (3), Andrea J. Liu (2) ((1) Institut fuer Theoretisc...
cond-mat.soft