Water Potential from Adaptive Force Matching for Ice and Liquid with Revised Dispersion Predicts Supercooled Liquid Anomalies in Good Agreement with Two Independent Experimental Fits

A revised version of the Water potential from Adaptive
force matching
for Ice and Liquid (WAIL) was developed by using the previous data
set for fitting the WAIL model but with a dispersion term calculated
using symmetry adapted perturbation theory (SAPT). The model has no
adjustable parameters and relies solely on fitting first-principles
information. The new model, named revised WAIL (rWAIL), shows improved
predictions of most properties of water when compared to the previously
published WAIL model. The rWAIL model also compares favorably to other
first-principles-derived water models, such as MB-Pol, at only a fraction
of the computational cost. The rWAIL model is used to study the properties
of supercooled water. The model shows evidence of a liquid–liquid
phase transition (LLPT) in the supercooled regimes with the liquid–liquid
critical point (LLCP) at 203 K and 90 MPa. This estimate is in good
agreement with a recent polynomial fit to the experimental density
of water. Also, the fit to the surface tension of supercooled water
based on the rWAIL model shows excellent agreement with the corresponding
fit to the experimental data. Consistent with previously published
molecular dynamics and experimental data, the surface tension of water
exhibits exponential growth in the supercooled regime, which is likely
a result of the emergence of a low-density liquid form of water. The
simulation thus unites two separate experimental fits with one first-principles-based
model, lending strong evidence of an LLPT in real water.