Understanding electrofreezing in water simulations.

Area of Science:

• Physical Chemistry
• Computational Physics
• Materials Science

Background:

• Understanding water's phase transitions, particularly freezing, is crucial in various scientific fields.
• External electric fields are known to influence the properties of polar molecules like water.
• The precise mechanism by which electric fields affect water freezing, especially ice nucleation, requires detailed investigation.

Purpose of the Study:

• To elucidate the role of external electric fields in promoting the freezing of liquid water.
• To quantify the effect of electric field strength on water's melting point and ice nucleation.
• To explore the underlying molecular interactions and structural changes responsible for field-induced freezing.

Main Methods:

• Utilized molecular dynamics simulations to model water behavior under external electric fields.
• Simulated water at a pressure of 1 bar with uniform electric fields of 1 V/nm and 2 V/nm.
• Analyzed changes in melting point, critical ice nucleus size, and local water structures.

Main Results:

• Applied electric fields significantly increase water's melting point (24 K for 1 V/nm, 44 K for 2 V/nm).
• The size of the critical ice nucleus decreases with increasing field strength due to elevated melting points.
• Ice nucleation occurred consistently at approximately 40 K below the field-dependent melting point, irrespective of field strength.

Conclusions:

• External electric fields promote water freezing by increasing the melting point and reducing the critical nucleus size.
• Polarized liquid water retains its characteristic local structures and anomalous properties, influencing nucleation dynamics.
• Results are pertinent to heterogeneous ice nucleation, where local surface fields can facilitate ice formation.