# Surface Hopping Molecular Dynamics Simulations for Photochemistry Involving Pyrene and CH3Cl

## TL;DR

This paper studies the photochemical reactions of pyrene and methyl chloride using simulations to understand their behavior and potential for creating functional materials.

## Contribution

The study introduces a computational approach combining surface hopping dynamics and quantum methods to explore photoreactions of pyrene and CH3Cl complexes.

## Key findings

- Excited-state lifetimes and photophysics of pyrene-CH3Cl complexes were determined using surface hopping simulations.
- Computational methods revealed structural and electronic properties of reactants and products in the photochemical process.
- The study provides insights into possible photochemical pathways for functionalized carbon-based materials.

## Abstract

Pure or halogenated polycyclic aromatic hydrocarbons
(PAHs) and
saturated halogenated hydrocarbons are both classes of harmful chemicals
found in Earth’s atmosphere, often involved in photochemical
reactions. On a positive side, the photoreaction of PAHs with halogenated
hydrocarbons serves as a model and offers routes to functionalized
nanostructured carbon-based materials with tailored optoelectronic
properties. Mechanistic studies on the photoreactions of these chemicals,
possibly with each other, are therefore clearly of interest but still
comparatively rare. In the present work, as a representative case
study, the photophysics (spectra, excited-state lifetimes) and photoreaction
dynamics of van der Waals or chemically bound complexes of pyrene
(C16H10) and methyl chloride (CH3Cl) were investigated using a combination of computational techniques,
thereby delivering time- and atom-resolved information on postexcitation
processes. Structural optimizations of possible reactants and products,
as well as excited states and absorption spectra, were obtained by
semiempirical (AM1) configuration interaction singles (CIS) and (time-dependent)
density functional theory (DFT), respectively. Nonadiabatic surface
hopping dynamics (NASH) based on AM1-CIS provided excited-state lifetimes
and were used to explore various photochemical channels of CH3Cl physisorbed or covalently bound to pyrene.