Advances in the Projected Forces and Momenta Decoherence Method for Attosecond Nonadiabatic Molecular Dynamics

Abstract

The Projected Forces and Momenta (PFM) decoherence correction has been recently introduced [J. Chem. Theory Comput. 2025, 21, 10645] and successfully applied for trajectory surface-hopping (TSH) simulations describing the coupled electron-nuclear dynamics originating from coherent superpositions of molecular electronic states generated by broadband laser excitation. In this work, we extend the capabilities of TSH-PFM for the simulation of a broader range of nonadiabatic dynamics. First, we showcase the inclusion of the explicit interaction with a non-perturbative broadband pulse and apply it to the LiH molecule, obtaining very good agreement with full quantum-mechanical reference calculations. We then demonstrate how a recently proposed post-processing approach to incorporate a posteriori initial electronic coherences onto pulse-independent TSH trajectories [J. Chem. Theory Comput. 2026, 22, 1224] allows for the evaluation of the dynamics arising from initial electronic coherences across a large manifold of perturbative few-fs UV pulses, without recalculating the nuclear dynamics for every set of parameters. This is exemplified for the glycine molecule, systematically varying the central frequency and bandwidth of the broadband excitation pulse. Finally, we scrutinize TSH-PFM for the ring-opening reaction in 1,2-dithiane. On the one hand, we show that TSH-PFM predicts the same nonadiabatic dynamics as established TSH approaches throughout the whole propagation of 700 fs. On the other hand, we find that an initial superposition of the two lowest excited states, albeit decoher- ing before the ring opens, accelerates the structural dynamics by several tens of fs compared to that starting exclusively from the lowest excited state due to the population of the second excited state.