An efficient decoherence scheme for fewest switches surface hopping method

The fewest switches surface hopping method, in its original form, is known to be over-coherent. An accurate and efficient decoherence scheme is still a question of concern in the community. We propose a modification of the augmented fewest switches surface hopping (A-FSSH) scheme to make it efficient without compromising on its accuracy. We compare our proposed decoherence scheme with a recently proposed parameter-free decoherence scheme by Wang and co-workers. We show that for all model systems investigated here, our scheme is as accurate as the original A-FSSH method while at least 30 times more efficient. The decoherence scheme of Wang is more than ten times more efficient than our scheme although it does not give accurate results in the limit of large diabatic coupling.