Ab Initio Nonadiabatic Dynamics with Coupled Trajectories: A Rigorous Approach to Quantum (De)Coherence

Area of Science:

• Quantum chemistry
• Theoretical chemistry
• Chemical dynamics

Background:

• Accurate simulation of excited-state dynamics is crucial for understanding chemical reactions.
• Existing methods like fewest-switches surface-hopping have limitations in capturing quantum coherence.

Purpose of the Study:

• To develop and validate a novel nonadiabatic molecular dynamics approach based on the exact factorization of the electron-nuclear wave function.
• To assess the ability of the new method to capture quantum decoherence effects.

Main Methods:

• Implementation of a coupled-trajectory mixed quantum-classical (CT-MQC) scheme derived from the exact factorization framework.
• Benchmarking CT-MQC against a revised fewest-switches surface-hopping method.
• Application to the gas-phase photochemistry (ring-opening) of oxirane.

Main Results:

• The CT-MQC scheme successfully captures quantum (de)coherence effects in excited-state dynamics.
• The new method demonstrates improved accuracy compared to the revised surface-hopping scheme, addressing its overcoherence issue.
• Detailed analysis of decoherence effects in oxirane photochemistry was performed.

Conclusions:

• The exact factorization framework provides a powerful tool for ab initio molecular dynamics simulations of nonadiabatic processes.
• The CT-MQC approach offers a robust and accurate method for studying excited-state dynamics, including quantum coherence.
• This work advances the simulation of photochemical reactions and related phenomena.