Solid-Liquid Interfacial Free Energy of Water:  A Molecular Dynamics Simulation Study

Area of Science:

• Physical Chemistry
• Computational Materials Science
• Thermodynamics

Background:

• Accurate estimation of solid-liquid interfacial free energy (γ) is crucial for understanding phase transitions in materials.
• Molecular dynamics (MD) simulations offer a powerful tool for probing interfacial properties at the atomic level.
• Previous studies have utilized various methods to determine γ for water models, with varying results.

Purpose of the Study:

• To calculate the solid-liquid interfacial free energy (γ) for two prominent water models: TIP4P-Ew and TIP5P-Ew.
• To validate the superheating-undercooling hysteresis method against established molecular dynamics simulation results.
• To compare computed γ values with experimental data for ambient pressure conditions.

Main Methods:

• Employed the superheating-undercooling hysteresis method combined with molecular dynamics (MD) simulations.
• Utilized two refined water models: TIP4P-Ew and TIP5P-Ew, suitable for Ewald summation techniques.
• Performed simulations at ambient pressure (1 bar).

Main Results:

• The calculated interfacial free energy (γ) was 37 mJ/m² for the TIP4P-Ew model.
• The calculated interfacial free energy (γ) was 42 mJ/m² for the TIP5P-Ew model.
• These values are consistent with a prior direct MD simulation (39 mJ/m²) and fall within the experimental range (25–44 mJ/m²).

Conclusions:

• The superheating-undercooling hysteresis method provides reliable estimates for the solid-liquid interfacial free energy of water models.
• Both TIP4P-Ew and TIP5P-Ew models yield interfacial free energy values that are in good agreement with experimental observations.
• This study confirms the applicability of MD simulations and the hysteresis method for accurate thermodynamic property calculations of water.