Decoherence and surface hopping: When can averaging over initial conditions help capture the effects of wave packet separation?

Journal Article · Sat Jan 01 04:00:00 EST 2011 · Journal of Chemical Physics

DOI:https://doi.org/10.1063/1.3603448· OSTI ID:1065649

Subotnik, Joseph E. ^[1]; Shenvi, Neil ^[2]

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1. Univ. of Pennsylvania, Philadelphia, PA (United States)
2. Duke Univ., Durham, NC (United States)

Fewest-switches surface hopping (FSSH) is a popular nonadiabatic dynamics method which treats nuclei with classical mechanics and electrons with quantum mechanics. In order to simulate the motion of a wave packet as accurately as possible, standard FSSH requires a stochastic sampling of the trajectories over a distribution of initial conditions corresponding, e.g., to the Wigner distribution of the initial quantum wave packet. Although it is well-known that FSSH does not properly account for decoherence effects, there is some confusion in the literature about whether or not this averaging over a distribution of initial conditions can approximate some of the effects of decoherence. In this paper, we not only show that averaging over initial conditions does not generally account for decoherence, but also why it fails to do so. We also show how an apparent improvement in accuracy can be obtained for a fortuitous choice of model problems, even though this improvement is not possible, in general. For a basic set of one-dimensional and two-dimensional examples, we find significantly improved results using our recently introduced augmented FSSH algorithm.

• Research Organization: Energy Frontier Research Centers (EFRC); Center for Solar Fuels (UNC EFRC)
• Sponsoring Organization: USDOE SC Office of Basic Energy Sciences (SC-22)
• DOE Contract Number: SC0001011
• OSTI ID: 1065649
• Journal Information: Journal of Chemical Physics, Journal Name: Journal of Chemical Physics Journal Issue: 24 Vol. 134 (24); ISSN 0021-9606
• Publisher: American Institute of Physics (AIP)
• Country of Publication: United States
• Language: English

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