Dissociation of polycyclic aromatic hydrocarbons: molecular dynamics studies

Area of Science:

• Physical Chemistry
• Astrochemistry
• Computational Chemistry

Background:

• Polycyclic Aromatic Hydrocarbons (PAHs) are abundant in space.
• PAH radical cations are important in interstellar environments.
• Understanding their dissociation is key to astrochemistry.

Purpose of the Study:

• Investigate dissociation dynamics of PAH radical cations.
• Determine branching ratios and kinetics of fragment formation.
• Explore size and energy dependence of dissociation pathways.

Main Methods:

• Molecular dynamics simulations.
• On-the-fly electronic structure calculations using SCC-DFTB.
• Benchmarking SCC-DFTB against DFT.

Main Results:

• Identified H and C2H2 (ethyne) as major dissociation fragments.
• Observed H/C2H2 ratio increases with PAH size and decreases with energy.
• For coronene at 30 eV, H loss is the dominant channel.

Conclusions:

• Dissociation trends align with experimental observations.
• Smaller internal energies and larger PAH sizes favor hydrogen loss.
• Provides insights into PAH fragmentation mechanisms in astrophysical settings.