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A "backtracking" correction for the fewest switches surface hopping algorithm
Gaohan Miao1, Xuezhi Bian1, Zeyu Zhou1
1Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA.
The Journal of Chemical Physics
|September 23, 2020
Summary
We introduce a backtracking correction to the fewest switches surface hopping (FSSH) algorithm. This method enhances accuracy for nuclear dynamics simulations, especially with complex electronic Hamiltonians, by reducing unnecessary quantum state hops.
Area of Science:
- Quantum chemistry
- Computational physics
- Chemical dynamics
Background:
- Surface hopping algorithms are crucial for simulating non-adiabatic dynamics.
- Tully's fewest switches surface hopping (FSSH) is a widely used method.
- Standard FSSH can struggle with accuracy in complex systems, particularly with complex-valued Hamiltonians.
Purpose of the Study:
- To improve the accuracy and reliability of the FSSH algorithm.
- To address the failure of standard FSSH with complex-valued electronic Hamiltonians.
- To introduce a computationally inexpensive correction to FSSH.
Main Methods:
- A novel "backtracking" mechanism is proposed for the FSSH algorithm.
- The method involves rewinding dynamics upon detection of consecutive hops.
- The modified algorithm is tested for nuclear dynamics in multidimensional configuration spaces.
Main Results:
- The backtracking correction significantly improves the accuracy of surface hopping.
- The enhanced FSSH method performs well even with complex-valued electronic Hamiltonians.
- The computational overhead of the backtracking mechanism is minimal.
Conclusions:
- The proposed backtracking correction makes surface hopping a more robust and accurate method for nuclear dynamics.
- This advancement is particularly important for systems described by complex-valued electronic Hamiltonians.
- Further investigation is warranted to assess the impact on real-valued Hamiltonians, including spin effects.
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