Testing the recent charge-on-spring type polarizable water models. II. Vapor-liquid equilibrium

Area of Science:

• Computational chemistry
• Molecular modeling
• Physical chemistry

Background:

• Accurate molecular models are crucial for simulating water's behavior.
• Polarization effects significantly influence water's thermodynamic properties.
• Existing models struggle to consistently describe vapor-liquid coexistence.

Purpose of the Study:

• To evaluate seven molecular water models based on the charge-on-spring (COS) method.
• To compare their ability to reproduce key thermodynamic properties and critical parameters.
• To assess the impact of polarization and model variations on water's vapor-liquid equilibrium.

Main Methods:

• Simulated vapor-liquid coexistence region for seven water models.
• Calculated second virial coefficient, heat of vaporization, vapor pressure, coexistence curve, and surface tension.
• Determined and compared critical temperatures, densities, and pressures.

Main Results:

• The high-temperature slope of the temperature-density (T-ρ) curve accurately predicts critical temperature.
• Gaussian charge distributions show advantages over point charges in describing the critical region.
• Nonpolarizable models fail to consistently describe vapor-liquid coexistence properties, even with correct critical temperatures.

Conclusions:

• Models incorporating field-dependent polarizability and variable size (BKd2, BKd3) offer improved descriptions.
• Gaussian charge distributions are superior for modeling water's critical phenomena.
• Accurate simulation of vapor-liquid coexistence requires polarizable models.