Ab-initio Dynamics of Rare Thermally Activated Reactions

TL;DR

This paper presents an efficient ab-initio framework combining quantum electronic and stochastic nuclear dynamics to study rare thermally activated reactions along dominant pathways, overcoming limitations of traditional molecular dynamics.

Contribution

It introduces a novel path integral-based method coupling quantum electronic states with Langevin dynamics for nuclear motion, enabling the study of rare reactions without extensive metastable state exploration.

Findings

Successfully characterized the dominant pathway in cyclobutene to butadiene reaction.

Demonstrated efficiency in simulating thermally activated reactions.

Method surpasses traditional ab-initio molecular dynamics in rare event sampling.

Abstract

We introduce a framework to investigate ab-initio the dynamics of rare thermally activated reactions. The electronic degrees of freedom are described at the quantum-mechanical level in the Born-Oppenheimer approximation, while the nuclear degrees of freedom are coupled to a thermal bath, through a Langevin equation. This method is based on the path integral representation for the stochastic dynamics and yields the time evolution of both nuclear and electronic degrees of freedom, along the most probable reaction pathways, without spending computational time to explore metastable states. This approach is very efficient and allows to study thermally activated reactions which cannot be simulated using ab-initio molecular dynamics techniques. As a first illustrative application, we characterize the dominant pathway in the cyclobutene to butadiene reaction.