Simulating Attochemistry: Which Dynamics Method to Use?

TL;DR

This paper evaluates the accuracy of common nonadiabatic dynamics methods in simulating attochemistry, revealing their limitations in capturing electronic coherence effects crucial for controlling photoproduct formation.

Contribution

It provides a systematic comparison of mixed quantum-classical approaches against high-accuracy quantum dynamics for attochemistry applications.

Findings

Mixed quantum-classical methods accurately reproduce average nuclear motion on a single electronic state.

These methods fail to capture nuclear motion driven by electronic coherence along the derivative coupling.

Quantum coherence effects are essential for accurate attochemistry simulations.

Abstract

Attochemistry aims to exploit the properties of coherent electronic wavepackets excited via attosecond pulses, to control the formation of photoproducts. Such molecular processes can in principle be simulated with various nonadiabatic dynamics methods, yet the impact of the approximations underlying the methods is rarely assessed. The performances of widely used mixed quantum-classical approaches, the Tully surface hopping, and classical Ehrenfest methods are evaluated against the high-accuracy DD-vMCG quantum dynamics. This comparison is conducted on the valence ionization of fluorobenzene. Analyzing the nuclear motion induced in the branching space of the nearby conical intersection, the results show that the mixed quantum-classical methods reproduce quantitatively the average motion of a quantum wavepacket when initiated on a single electronic state. However, they fail to properly capture the nuclear motion induced by an electronic wavepacket along the derivative coupling, the latter originating from the quantum electronic coherence property -- key to attochemistry.