Figure shows the density-temperature isobars obtained using a Langevin thermostat (friction coecient 2 ps -1 ) and parallel tempering for 128 molecules (for details we refer to Ref. ). In most of the paralleltempering simulations, we see that images at low temperatures tend to stop exchanging with images at higher temperatures and freeze at the same time. Although the structure of ordered ice is not recovered, we nd that the density around 210 K is always very close to the density of hexagonal ice reported in Tab. II. This can also be seen in Fig. where we show the dierence in density between ice and water along the isobar. Therefore, we believe that these structures are best categorized as precursors of low-density amorphous ice .