Equation of State of Supercooled Water from the Sedimentation Profile
  To study the coexistence of two liquid states of water within one simulation box, we implement an equilibrium sedimentation method--which involves applying a gravitational field to the system and measuring/calculating the resulting density profile in equilibrium. We simulate a system of particles interacting via the ST2 potential, a model for water. We detect the coexistence of two liquid phases at low temperature. 
M. Yamada, H.E. Stanley and F. Sciortino