From the ideal gas to an ideal glass: reversible path to random close   packing
  A reproducible RCP state is obtained by a well-defined rate process, which is first-order in free volume, starting from an equilibrium thermodynamic state of the hard-sphere fluid. The RCP state is also reproduced by a thermodynamic pathway that inhibits the frequent production of small crystal nucleites which can lead to heterogeneities at close packing. The simple-cubic single-occupancy (SCSO) cell system, in which crystallization is de facto prohibited, provides a reversible path all the way from the ideal gas to the ideal glass (RCP). By such a route, unique characterization of RCP becomes possible. 
Leslie V. Woodcock