Molecular Dynamics Simulations of Reactions between Molecules: High-Energy Particle Bombardment of Organic Films

The high-energy particle bombardment of a molecular film adsorbed upon a metal substrate has been investigated via molecular dynamics computer simulations with an empirical many-body potential energy function constructed for studying reactive dynamics. The specific system modeled is the bombardment of an ethylidyne (C₂H₃) overlayer adsorbed on Pt{lll} by a 500-eV Ar atom beam. Approximately 80% of the ejected hydrocarbon species originate from a single C₂H₃ adsorbate, while the others result from reactions between two C₂H₃ adsorbates. A study of the internal energies of all of the ejected hydrocarbon aggregates reveals that those originating from a single C₂H₃ adsorbate are generally stable to any further fragmentation or rearrangement. Examples of commnn ejection mechanisms for species which originate from a single adsorbate, such as CH₃, C₂H₃, or HCCH, and those which originate from moee than one adsorbate, such as CH₄, are given.