CCl(4) dissociation on the ice I(h) surface: an excess electron mediated process

Area of Science:

• Atmospheric Chemistry
• Surface Science
• Quantum Chemistry

Background:

• Chlorofluorocarbon (CFC) dissociation in the atmosphere is a critical heterogeneous process, primarily occurring on ice particle surfaces.
• Recent studies indicate that excess electrons can significantly enhance CFC dissociation rates, supported by theoretical and experimental evidence.

Purpose of the Study:

• To investigate the mechanism and energetics of carbon tetrachloride (CCl4) dissociation on ice surfaces induced by excess electrons.
• To elucidate the atomistic pathway of CCl4 dissociation and chloride ion interaction with the ice surface.

Main Methods:

• Density Functional Theory (DFT) calculations to determine energy changes during CCl4 dissociation.
• Ab initio molecular dynamics simulations to reveal the atomistic pathway of the dissociation process.

Main Results:

• DFT calculations show an energy gain of 0.8 eV for CCl4 dissociation on an ice surface with an excess electron, compared to the gas phase.
• Ab initio molecular dynamics revealed a pathway involving the capture of Cl(-) by the ice surface via partial solvation.

Conclusions:

• Excess electrons facilitate CCl4 dissociation on ice surfaces with a notable energy gain.
• The dissociation pathway involves chloride ion capture and partial solvation, aligning with experimental observations and providing atomistic insight into atmospheric CFC degradation.