Decoherence-induced adaptive multiconfigurational Ehrenfest dynamics for nonadiabatic scattering simulations

Abstract

Theoretical simulation of nonadiabatic scattering dynamics involves delicate treatment of both electronic coherence and decoherence all the time. In this study, we investigate the multiconfigurational Ehrenfest (MCE) dynamics with adaptive basis set expansion to capture the growing entanglement between the electronic states and the nuclear degrees of freedom with time, which shares the same features with the well-known overcoherence problem in the traditional Ehrenfest mean field method. Inspired by the decoherence studies in the framework of mixed quantum–classical dynamics, we here propose a decoherence-induced adaptive MCE (DA-MCE) method, which can deal with the coherent propagation and quantum decoherence in nonadiabatic scattering dynamics simultaneously. As demonstrated in the three famous Tully models, DA-MCE can efficiently capture the time evolution of the reduced density matrix, the Stueckelberg interference, and the rapid decoherence. In particular, both the adaptive expansion of the basis set and the form of the variational Ansatz are found to be highly important for the description of complex dynamics. Compared to the multiconfigurational surface hopping method proposed recently, our DA-MCE can also be regarded as a multiconfigurational version of the branching corrected mean field method, which indicates the potential combination of general mixed quantum–classical trajectories with the proposed multiconfigurational approach.