FSSH-2: Fewest Switches Surface Hopping with Robust Switching Probability 

Population of the second adiabatic state for the Tully 1 model using FSSH (left) and FSSH-2 (right) for different numbers of substeps.

L. Araujo, C. Lasser, and B. Schmidt

This study introduces the FSSH-2 scheme, a redefined and numerically stable adiabatic Fewest Switches Surface Hopping (FSSH) method. It reformulates the standard FSSH hopping probability without non-adiabatic coupling vectors and allows for numerical time integration with larger step sizes. The advantages of FSSH-2 are demonstrated by numerical experiments for five different model systems in one and two spatial dimensions with up to three electronic states. 

J. Chem. Theo. Comp. 29 (9), 3413-3419 (2024)
Data available at 10.5281/zenodo.10497421