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

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journal contribution
posted on 16.06.2017, 00:00 by Seung Kyu Min, Federica Agostini, Ivano Tavernelli, E. K. U. Gross
We report the first nonadiabatic molecular dynamics study based on the exact factorization of the electron–nuclear wave function. Our approach (a coupled-trajectory mixed quantum–classical, CT-MQC, scheme) is based on the quantum–classical limit derived from systematic and controlled approximations to the full quantum-mechanical problem formulated in the exact-factorization framework. Its strength is the ability to correctly capture quantum (de)­coherence effects in a trajectory-based approach to excited-state dynamics. We show this by benchmarking CT-MQC dynamics against a revised version of the popular fewest-switches surface-hopping scheme that is able to fix its well-documented overcoherence issue. The CT-MQC approach is successfully applied to investigation of the photochemistry (ring-opening) of oxirane in the gas phase, analyzing in detail the role of decoherence. This work represents a significant step forward in the establishment of the exact factorization as a powerful tool to study excited-state dynamics, not only for interpretation purposes but mainly for nonadiabatic ab initio molecular dynamics simulations.