Liquid-liquid criticality in the WAIL water model

Area of Science:

• Physical Chemistry
• Computational Chemistry
• Materials Science

Background:

• The anomalous behavior of liquid water is a long-standing puzzle in physical chemistry.
• A leading hypothesis suggests a second critical point exists in deeply supercooled water.
• Previous studies used classical models, necessitating further validation with more advanced models.

Purpose of the Study:

• To rigorously demonstrate the existence of a liquid-liquid critical point in supercooled water.
• To test the robustness of this critical point in a flexible and polarizable water model.
• To provide stronger numerical evidence supporting the two-liquid hypothesis for water.

Main Methods:

• Utilized the Water Model with Ab Initio Liquids (WAIL) model, parameterized using ab initio calculations.
• Incorporated flexibility and polarizability into the water model, accounting for key physical effects.
• Performed numerical simulations to locate the liquid-liquid critical point.

Main Results:

• Successfully located a liquid-liquid critical point within the WAIL model of water.
• The critical point was found robustly, even with parameters derived solely from quantum ab initio calculations.
• The model's flexibility and polarizability significantly influenced the phase behavior.

Conclusions:

• The existence of a liquid-liquid critical point is a robust feature of supercooled water's free energy landscape.
• This finding strongly supports the hypothesis that water can exist as two distinct liquid states.
• Advanced models incorporating quantum mechanical effects are crucial for understanding water's complex phase behavior.