Longitudinal and transverse collective dynamics in water by simulation using the BK3 model

Area of Science:

• Condensed matter physics
• Physical chemistry
• Computational physics

Background:

• Understanding collective dynamics in liquid water is crucial for various scientific disciplines.
• Previous models often neglect the polarizability of water molecules, limiting accuracy.

Purpose of the Study:

• To explore collective dynamic modes in liquid water using a polarizable water model.
• To investigate the influence of polarizability and molecular mass on these dynamics.
• To quantitatively describe excitation modes using the Generalized Collective Modes (GCMs) model.

Main Methods:

• Molecular dynamics (MD) simulations were performed using the BK3 polarizable water model.
• The dynamic structure factor and current correlation spectral densities were computed.
• Atom-atom partial correlation functions were fitted using the Generalized Collective Modes (GCMs) model.

Main Results:

• The study successfully computed dynamic properties of liquid water across a wide frequency range.
• Comparison between BK3 and SPC/E water models highlighted the effect of polarizability.
• Analysis of ambient water and heavy water revealed the impact of molecular mass on collective dynamics.
• The GCMs model provided a quantitative description of excitation modes, including frequencies and damping coefficients.

Conclusions:

• Polarizability significantly influences the collective dynamics of liquid water.
• Molecular mass also plays a role in collective dynamics, as evidenced by heavy water simulations.
• The GCMs model offers a robust framework for analyzing and understanding water's dynamic excitations.