Abstract
Deeply supercooled water droplets held container-less in an acoustic levitator are investigated with high energy X-ray scattering. The temperature dependence X-ray structure function is found to be non-linear. Comparison with two popular computer models reveals that structural changes are predicted too abrupt by the TIP5P model, while the rate of change predicted by TIP4P is in much better agreement with experiment. The abrupt structural changes predicted by the TIP5P model to occur in the temperature range between 260-240K as water approaches the homogeneous nucleation limit are unrealistic. Both models underestimate the distance between neighbouring oxygen atoms and overestimate the sharpness of the OO distance distribution, indicating that the strength of the H-bond is overestimated in these models.
