Density maximum and polarizable models of water

Area of Science:

• Physical Chemistry
• Computational Chemistry
• Materials Science

Background:

• Accurate prediction of water's density-temperature relationship, including its maximum density at 4 °C, is a critical benchmark for molecular models.
• Existing nonpolarizable models can approximate this behavior, but polarizable models face significant challenges in reproducing this property accurately.

Purpose of the Study:

• To investigate the difficulties in modeling water's density-temperature behavior with polarizable models.
• To present a modified BK model capable of accurately predicting water density over a wide temperature range.
• To improve the description of molecular interactions and polarization effects in water models.

Main Methods:

• Overview of existing molecular models' performance on ρ-T diagrams.
• Development of a new version of the BK model using the charge-on-spring method with three Gaussian charges.
• Incorporation of repulsion and attraction forces as functions of the induced dipole moment, alongside dipole-dependent dispersion forces.

Main Results:

• The modified BK model accurately predicts the density-temperature function of water.
• The model generates accurate dipole distributions, leading to a precise estimation of the liquid's dielectric constant.
• The approach addresses the challenges of modeling polarizable systems for water properties.

Conclusions:

• The modified BK model provides a robust framework for simulating water's thermophysical properties.
• The inclusion of dipole-dependent intermolecular forces is crucial for accurately capturing water's unique density behavior.
• This work advances the development of accurate polarizable molecular models for water.