Atomistic Simulations of Fe(CO)₅ Fragmentation Dynamics on a Substrate

The dissociation of organometallic molecules upon ionization by electron impact is one of the key fundamental processes behind nanofabrication using focused electron beams. The degree of molecular fragmentation (i.e., the number of volatile ligands produced) and the dynamics of this process are important factors affecting the elemental composition and metal content of the resulting deposits. This study presents results of irradiation-driven molecular dynamics (IDMD) simulations of the irradiation-induced fragmentation of iron pentacarbonyl, Fe-(CO)₅, physisorbed on several different experimentally relevant substrates: crystalline Au(111) and Au(100), polycrystalline gold, and amorphous carbon. The employed computational approach enables the simulation of covalent bond breaking in the deposited molecule alongside the explicit dynamics of the substrate. We demonstrate that the fragmentation dynamics of Fe-(CO)₅ is similar across the considered substrates but is influenced by the strength of its binding to the substrate and by the structural irregularity of the substrate, which enables the molecule to adopt various orientations. The results of this study have implications for atomistic simulations of nanostructure formation using focused electron beams and for the interpretation of surface-science experiments involving the irradiation of molecular systems with electron beams.