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Measuring Light-Switching Behavior Using an Occupancy and Light Data Logger

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Revisiting the Recoherence Problem in the Fewest Switches Surface Hopping Algorithm.

Gaohan Miao¹, Joseph Subotnik¹

¹Department of Chemistry , University of Pennsylvania , Philadelphia , Pennsylvania 19104 , United States.

The Journal of Physical Chemistry. A

|June 11, 2019

Summary

Tully's fewest switches surface hopping algorithm fails at avoided crossings due to issues with nuclear momentum. Correcting these failures requires non-local time dynamics or interacting trajectories.

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Area of Science:

Quantum chemistry
Chemical dynamics
Computational modeling

Background:

Surface hopping algorithms approximate quantum dynamics.
Tully's fewest switches (FSSH) is a widely used method.
FSSH struggles with wave packet "recoherence" at avoided crossings.

Purpose of the Study:

To identify the precise failure mechanisms of FSSH.
To analyze FSSH performance at one-dimensional avoided crossings.
To investigate the role of nuclear momenta versus electronic populations.

Main Methods:

Utilized two distinct one-dimensional avoided crossing models.
Employed an initial wave function as a superposition of wave packets.
Analyzed asymptotic nuclear momenta and electronic populations.

Main Results:

FSSH failures are linked to asymptotic nuclear momenta, not electronic populations.
Failures originate from the assumption of independent, time-local trajectories.
Recoherence of wave packets exacerbates FSSH inaccuracies.

Conclusions:

The fundamental assumptions of FSSH are insufficient for accurate dynamics at avoided crossings.
Correcting FSSH requires incorporating time-nonlocal dynamics or inter-trajectory interactions.
The study highlights limitations of FSSH in specific quantum dynamical scenarios.