Role of the Molecular Environment in Quenching the Irradiation-Driven Fragmentation of Fe(CO)₅: A Reactive Molecular Dynamics Study

Abstract

Irradiation-driven fragmentation and chemical transformations of molecular systems play a key role in nanofabrication processes where organometallic compounds break up due to the irradiation with focused particle beams. In this study, reactive molecular dynamics simulations have been performed to analyze the role of the molecular environment on the irradiation-induced fragmentation of molecular systems. As a case study, we consider the dissociative ionization of iron pentacarbonyl, Fe(CO) 5 , a widely used precursor molecule for focused electron beam-induced deposition. In connection to recent experiments, the irradiationinduced fragmentation dynamics of an isolated Fe(CO) 5 + molecule is studied and compared with that of Fe(CO) 5 + embedded into an argon cluster. The appearance energies of different fragments of isolated Fe(CO) 5+ agree with the recent experimental data. For Fe(CO) 5 + embedded into an argon cluster, the simulations reproduce the experimentally observed suppression of Fe(CO) 5 + fragmentation and provide an atomistic-level understanding of this effect. Understanding irradiation-driven fragmentation patterns for molecular systems in environments facilitates the advancement of atomistic models of irradiation-induced chemistry processes involving complex molecular systems.

Condensed Matter Systems Exposed to Radiation: Multiscale Theory, Simulations, and Experiment

“…As an extension of the nonreactive CHARMM force field, rCHARMM is directly applicable to organic and biomolecular systems. , Its combination with many other pairwise and many-body force fields enables simulations of thermally driven and postirradiation chemical transformations in various molecular and condensed matter systems while monitoring their molecular composition and topology changes. , Due to its versatility and universality, the rCHARMM force field has been applied to study a broad range of processes and phenomena, including collision-induced structural transformations and fragmentation (in the gas phase or after the collision with surfaces); collision-induced fragmentation of molecular and cluster systems in the gas phase and placed in molecular environments; ,,, thermally driven and collision-induced chemistry of condensed systems, particularly water; , and surface chemistry processes lying in the core of modern nanofabrication techniques ,, (see a case study in section ). An extended description of the applications of this methodology can be found in recent reviews. , …”

“…Examples of clusters recently used for mimicking various environments. (a) Microhydrated thymine, (b) Fe­(CO) 5 embedded into a large argon cluster, and (c) multiple benzene molecules adsorbed on a water cluster as a model system for interstellar ice nanoparticle . The individual panels are scaled arbitrarily.…”

“…Copyright 2014 AIP Publishing. Panel (b) is reproduced from ref . Copyright 2023 American Chemical Society.…”

“…However, upon clustering, the fragmentation degree is considerably suppressed: the dominant channel is the removal of only two ligands from the FeCO 5 + molecule . The reactive MD approach (see section ) has elucidated the mechanism of the quenching of excess energy of the hot FeCO 5 + cation by the molecular environment. Such quenching alters the view of the elementary mechanisms that play a role in the FEBID process.…”

Electron-induced ligand loss from iron tetracarbonyl methyl acrylate

“…The gas-phase studies have been complemented by surface-based investigations, where the electron-induced ligand loss has been probed by XPS [ 13 ], ion desorption [ 14 ], IR spectroscopy [ 15 ], or cluster-beam studies [ 16 – 18 ]. The ligand loss has also been probed by ion impact, both in the gas phase [ 19 ] and on the surface [ 13 ], and, theoretically, by advanced reactive force field molecular dynamics simulations [ 20 ].…”