Next, we explore the properties of condensed water at various temperatures. We performed NPT classical MD simulations at P = 1 atm with temperatures from 238 K to 340 K, which spans the region from supercooled to room-temperature water liquid water. The calculated densities of liquid water are shown in Figure in comparison with MB-pol data and experimental measurements. As seen, the q-AQUA-pol results agree excellently with the corresponding experimental values in high temperature region. When the temperature decreases, the exists differences between q-AQUA-pol and experiment. However, the overall trend agrees well with experiment and the estimated temperature of maximum density is between 268-278 K, closer to the experimental maximum at 277 K. Such behavior outperforms MB-Pol which has larger disagreement with experiment and lower temperature of maximum density. The difference between q-AQUA-pol and experimental densities can be partly attributed to the neglect of nuclear quantum effects (NQE) in classical MD sim-ulations, which has been shown to be important. We conducted PIMD NPT simulations at 288 K, 298 K, and 320 K to investigate the effect of NQE on densities. As shown in the red diamond data in Figure , when the nuclear quantum effects are included, the predicted densities decreases and excellent agreement with experiment is achieved for all these three temperatures. It is satisfying to see that the two sets of results appear to merge at higher temperatures. The error bars shown for the q-AQUA-pol results come from the density vs time plots. These are shown in Fig. of the Supporting Information, which extends to 1 ns of the trajectory. It can be reasonably inferred that liquid water densities from q-AQUA-pol can be improved with NQE included, resulting in better agreement with experiment. The temperature dependence of the order parameter 58 is shown in Figure . As seen, the distribution narrows as the temperature decreases into the supercooled liquid regime. That cold water, i.e., ice, assumes a tetrahedral H-bonding motif can be traced at least to Bernal and Fowler. The ridge at ≈ 0.5 is interesting; however, it is beyond the scope of this paper to investigate this in detail. Some discussion of it can be found in a recent paper where the order parameter obtained with MB-pol was reported.