Dynamic mesoscale model of dipolar fluids via fluctuating hydrodynamics

Area of Science:

• Mesoscopic physics
• Computational chemistry
• Molecular dynamics

Background:

• Fluctuating hydrodynamics (FHD) is a mesoscopic simulation framework.
• Current FHD models lack explicit representation of electrical forces.
• Accurate simulation of electrical forces is crucial for molecular systems.

Purpose of the Study:

• To develop a novel mesoscopic model incorporating electrical forces.
• To create the ϕ-FHD equations by coupling dipole moment dynamics with electrostatics.
• To enable simulations of molecular systems with integrated electrostatic and hydrodynamic interactions.

Main Methods:

• Devised an Ansatz for dipole moment density dynamics linked to the Poisson equation.
• Coupled these dynamics with existing FHD equations to form ϕ-FHD.
• Validated the model by simulating water dielectric function and ion hydration free energies.
• Mapped field variables from all-atom molecular dynamics (AAMD) simulations.

Main Results:

• The new ϕ-FHD equations accurately capture electrostatic interactions.
• Mesoscopic simulations using ϕ-FHD precisely predicted water dielectric function and ion hydration free energies.
• Model parameters can be derived from finer-grained AAMD simulations.
• Achieved a spatial resolution of 5 Å.

Conclusions:

• The ϕ-FHD model provides a robust platform for mesoscopic simulations including electrostatics.
• It accurately models emergent behaviors in molecular systems at intermediate scales.
• Offers a valuable semi-explicit solvent model for complex systems like biomolecular machines and nanofluidics.