Photo-induced reactions from efficient molecular dynamics with electronic transitions using the FIREBALL local-orbital density functional theory formalism

TL;DR

This paper introduces a molecular dynamics method with electronic transitions within the FIREBALL density functional theory framework, enabling detailed simulation of photo-induced reactions in large molecular systems.

Contribution

The authors developed and implemented a new algorithm for simulating photo-induced processes with electronic transitions in a local-orbital DFT code, allowing large ensemble reaction profile calculations.

Findings

Identified multiple deactivation channels depending on electronic transition timing.

Successfully simulated [2+2] cycloaddition and photo-induced polymerization reactions.

Provided insights into the electronic state changes during photo-reactions.

Abstract

The computational simulation of photo-induced processes in large molecular systems is a very challenging problem. Here, we present a detailed description of our implementation of a molecular dynamics with electronic transitions algorithm within the local-orbital density functional theory code Fireball, suitable for the computational study of these problems. Our methodology enables simulating photo-induced reaction mechanisms over hundreds of trajectories; therefore, large statistically significant ensembles can be calculated to accurately represent a reaction profile. As an example of the application of this approach, we report results on the [2+2] cycloaddition of ethylene with maleic anhydride and on the [2+2] photo-induced polymerization reaction of two C60 molecules. We identify different deactivation channels of the initial electron excitation, depending on the time of the electronic transition from LUMO to HOMO, and the character of the HOMO after the transition.