Divide-and-Conquer-Type Density-Functional Tight-Binding Molecular Dynamics Simulations of Proton Diffusion in a Bulk...

Area of Science:

• Computational Chemistry
• Physical Chemistry
• Materials Science

Background:

• Proton diffusion in liquid water is crucial for many chemical and biological processes.
• Understanding proton transport mechanisms, like vehicular and Grotthuss diffusion, is essential.
• Previous computational methods faced limitations in accuracy or efficiency for large systems.

Purpose of the Study:

• To investigate proton diffusion in liquid water using advanced computational techniques.
• To accurately determine diffusion coefficients and energy barriers for different proton transport mechanisms.
• To validate a novel computational approach for simulating proton dynamics.

Main Methods:

• Employed molecular dynamics (MD) simulations combined with the divide-and-conquer-type density-functional tight-binding (DC-DFTB) method.
• Utilized a moderately large unit cell containing 523 water molecules and one excess proton.
• Validated the accuracy and computational efficiency of the DC-DFTB-MD approach.

Main Results:

• Successfully reproduced diffusion coefficients for both vehicular and Grotthuss proton diffusion processes.
• Calculated energy barriers for Grotthuss diffusion showed excellent agreement with experimental data.
• Demonstrated the effectiveness of the DC-DFTB-MD method for simulating proton transport in water.

Conclusions:

• The DC-DFTB-MD approach with a 523-water-molecule unit cell provides accurate simulations of proton diffusion in liquid water.
• This method accurately captures both vehicular and Grotthuss transport mechanisms.
• The study provides reliable computational data for proton diffusion energy barriers, consistent with experimental findings.