Simulating Attochemistry: Which Dynamics Method to Use?

Area of Science:

• Quantum dynamics
• Attochemistry
• Computational chemistry

Background:

• Attochemistry seeks to control molecular reactions using coherent electronic wavepackets generated by attosecond pulses.
• Nonadiabatic dynamics methods are used to simulate these molecular processes, but their approximations are often unevaluated.
• Assessing the accuracy of these simulation methods is crucial for advancing attochemistry.

Purpose of the Study:

• To evaluate the performance of common mixed quantum-classical methods against a high-accuracy quantum dynamics method.
• To assess the impact of approximations in simulating attochemical processes.
• To understand the limitations of current simulation techniques in capturing key quantum phenomena.

Main Methods:

• Comparison of Tully surface hopping and classical Ehrenfest methods with the DD-vMCG quantum dynamics method.
• Simulation of valence ionization of fluorobenzene.
• Analysis of nuclear motion in the branching space of a conical intersection.

Main Results:

• Mixed quantum-classical methods accurately reproduce average nuclear motion initiated on a single electronic state.
• These methods fail to capture nuclear motion induced by electronic wavepackets along derivative coupling.
• The failure is attributed to the inability to model quantum electronic coherence, a key aspect of attochemistry.

Conclusions:

• Widely used mixed quantum-classical methods have limitations in simulating attochemical processes.
• Accurate simulation of attochemistry requires methods that capture quantum electronic coherence.
• Further development of theoretical methods is needed to fully exploit attochemistry's potential.