Hydrogen-bond dynamics in the air-water interface.

Area of Science:

• Physical Chemistry
• Surface Science
• Computational Chemistry

Background:

• Hydrogen bonds (H-bonds) are crucial for water's properties.
• Understanding H-bond dynamics at interfaces is key to many chemical and biological processes.
• Previous studies suggest different H-bond dynamics in bulk water versus interfaces.

Purpose of the Study:

• To investigate hydrogen-bond dynamics at the air-water interface.
• To compare interface H-bond dynamics with those in bulk water.
• To elucidate the role of translational diffusion and polarization effects.

Main Methods:

• Molecular dynamics (MD) simulations were employed.
• Analysis focused on hydrogen-bond breaking and forming events.
• Simulations utilized polarizable and fixed-charge water models.

Main Results:

• Hydrogen-bond dynamics are faster at the air-water interface compared to bulk water for polarizable models, attributed to faster translational diffusion.
• When translational diffusion effects are removed, H-bond dynamics become slower at the interface.
• The reduced number of adjacent water molecules in the interface hinders H-bond acceptance/donation.
• Polarization effects appear significant at the water-vapor interface.

Conclusions:

• Translational diffusion significantly influences observed H-bond dynamics at the air-water interface.
• Interface-specific structural constraints lead to slower intrinsic H-bond dynamics compared to bulk water.
• Polarizable water models are essential for accurately capturing H-bond dynamics at the water-vapor interface.