Clusters of classical water models.

Area of Science:

• Computational Chemistry
• Molecular Dynamics
• Physical Chemistry

Background:

• Water cluster properties serve as critical benchmarks for molecular simulation models.
• Understanding low-energy configurations is essential for accurate water modeling.

Purpose of the Study:

• To identify and analyze low-energy water cluster configurations using various simulation models.
• To evaluate the performance of different water models, including polarizable and nonpolarizable ones, against experimental and quantum chemical data.

Main Methods:

• Systematic search for minimal energy configurations of water clusters (dimer to hexamer).
• Enumeration of hydrogen bonds and calculation of overlap integrals to identify distinct structures.
• Simulation using multiple water models: BSV, DC, GCP, SWM4-DP, SWM4-NDP, SPC-FQ, TIP4P-FQ, SPC/E, TIP4P, TIP4P-EW, TIP4P/2005, TIP5P, and flexible SPC.

Main Results:

• Identified an increasing number of topologically distinct, low-energy arrangements for clusters from dimer to hexamer.
• Model performance varied significantly based on charge placement and polarization treatment; TIP4P variants showed similar results, as did BSV/DC and SWM4-DP/SWM4-NDP.
• Spherical polarization was found to be crucial, with planar polarization models (SPC-FQ, TIP4P-FQ) favoring different arrangements.
• The GCP model demonstrated the best overall agreement with quantum mechanical calculations.

Conclusions:

• The placement of negative charge and the type of polarization (spherical vs. planar) critically influence water cluster structures.
• Vibrations have a minor impact on geometry but reduce internal energy.
• The GCP model is recommended for accurate simulations of water clusters and related phenomena.