A first principles simulation of rigid water.

Area of Science:

• Computational chemistry
• Molecular dynamics simulations
• Physical chemistry

Background:

• Car-Parrinello (CP) simulations are crucial for studying molecular behavior.
• Simulating water requires balancing accuracy with computational cost.
• Longer time scales are needed for complex phenomena like hydrophobic solvation.

Purpose of the Study:

• To investigate the impact of a rigid molecule approximation on CP simulations of water.
• To enable longer time scales in ab initio simulations of aqueous systems.
• To improve the accuracy of simulated structural properties and diffusion coefficients.

Main Methods:

• Car-Parrinello (CP) simulations were performed on water at ambient and high-pressure conditions.
• A rigid molecule approximation was employed, fixing intramolecular geometry.
• Larger time steps were utilized, allowing access to longer simulation timescales.

Main Results:

• The rigid water model yielded structural properties and diffusion coefficients in better agreement with experimental data compared to flexible simulations.
• The use of a rigid approximation allowed for significantly longer accessible simulation timescales.
• The method proved effective for ab initio simulations of aqueous solutions without chemical reactions or dissociation.

Conclusions:

• Employing a rigid molecule approximation in Car-Parrinello simulations of water enhances agreement with experimental results.
• This approach is a viable strategy for extending the accessible timescales in ab initio simulations of aqueous solutions.
• The findings suggest potential for more accurate modeling of complex solvation phenomena.