Non-conformal coarse-grained potentials for water.

Area of Science:

• Computational chemistry
• Materials science
• Chemical physics

Background:

• Modeling water accurately and efficiently is a significant challenge.
• Coarse-grained models offer computational advantages but require careful parameterization.
• Existing models often struggle with transferability across different thermodynamic conditions.

Purpose of the Study:

• To develop and evaluate coarse-grained water models using approximate non-conformal and generalized Stockmayer potentials.
• To assess the transferability of these models across various temperatures and pressures.
• To determine the necessary complexity for accurate and transferable water models.

Main Methods:

• Fitting single-particle coarse-grained potentials to the radial distribution function and liquid-gas density profile of the atomistic extended simple point charge (SPC/E) model.
• Utilizing downhill simplex optimization for parameter fitting.
• Comparing the developed models against established potentials like monatomic water (mW) and ELBA, and direct iterative Boltzmann inversion of SPC/E.

Main Results:

• Symmetrical potentials were found to be non-transferable, requiring re-parametrization for new state points.
• The addition of a point dipole alone was insufficient to ensure accuracy and transferability across temperatures (300 K-500 K) and pressures.
• Achieving transferability necessitates careful selection of target properties during model optimization.

Conclusions:

• Simple coarse-grained water models with symmetrical potentials lack transferability.
• Enhanced model complexity, beyond simple potentials and point dipoles, is likely required for transferable water models.
• The choice of target properties during optimization critically influences model accuracy and transferability.