N₂O₅ at water surfaces: binding forces, charge separation, energy accommodation and atmospheric implications

Area of Science:

• Atmospheric Chemistry
• Physical Chemistry
• Surface Science

Background:

• Interactions of dinitrogen pentoxide (N2O5) with water are crucial in atmospheric chemistry.
• Microscopic understanding of N2O5 properties at water surfaces and in bulk remains limited.

Purpose of the Study:

• To investigate the physical properties of N2O5 at water interfaces and in bulk water.
• To elucidate the microscopic basis of N2O5-water interactions.
• To provide insights into N2O5 behavior relevant to atmospheric processes.

Main Methods:

• Ab initio molecular dynamics simulations.
• Potential of mean force calculations.
• Analysis of N2O5-water collisions, binding energies, and free energy profiles.

Main Results:

• N2O5 collides with water surfaces and is trapped for at least 20 ps with 95% probability.
• No hydrolysis, evaporation, or bulk entry occurs during this trapping period.
• Significant charge separation fluctuations within N2O5 and picosecond-scale energy accommodation at the surface were observed.
• N2O5 exhibits a propensity for the aqueous surface with a free energy barrier of 1.8 kcal mol-1 for entry into the bulk.

Conclusions:

• N2O5 displays surface-trapping behavior at water interfaces, influencing its atmospheric reactivity.
• The findings offer a microscopic explanation for experimental observations in atmospheric chemistry.
• This study enhances the understanding of N2O5 partitioning and transformation in the atmosphere.