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Nonlocal STM Manipulation of Chlorobenzene on Si(111)‑7 × 7: Potentials, Kinetics, and First-Principles Molecular Dynamics Calculations for Open Systems

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posted on 26.05.2021, 14:46 authored by Tina Gaebel, Daniel Bein, Daniel Mathauer, Manuel Utecht, Richard Palmer, Tillmann Klamroth
We use quantum chemical cluster models together with constrained density functional theory (DFT) and ab initio molecular dynamics (AIMD) for open system to simulate and rationalize nonlocal scanning tunneling microscope (STM) manipulation experiments for chlorobenzene (PhCl) on a Si(111)-7 × 7 surface. We consider three different processes, namely, the electron-induced dissociation of the carbon–chlorine bond for physisorbed PhCl molecules at low temperatures and the electron- or hole-induced desorption of chemisorbed PhCl at 300 K. All processes can be induced nonlocally, i.e., up to several nanometers (nm) away from the injection site, in STM experiments. We rationalize and explain the experimental findings regarding the STM-induced dissociation using constrained DFT. The coupling of STM-induced ion resonances to nuclear degrees of freedom is simulated with AIMD using the Gadzuk averaging approach for open systems. From this data, we predict a 4 fs lifetime for the cationic resonance. For the anion model, desorption could not be observed. In addition, the same cluster models are used for transition-state theory calculations, which are compared to and validated against time-lapse STM experiments.