Quantum Dynamics\nfrom Classical Trajectories

Nonadiabatic\nmolecular dynamics plays an essential role\nin exploring\nthe time evolution of molecular systems. Various methods have been\ndeveloped for this study, with varying accuracy and computational\ncost. One very successful among them is trajectory surface hopping,\nwhich propagates nuclei as classical trajectories using forces from\na quantum description of the electrons and incorporates nonadiabatic\neffects through stochastic state changes during each trajectory propagation.\nA statistical analysis of an ensemble of the independent trajectories\nrecovers the simulated system’s behavior. This approach can\ngive good results, but it is known to overlook nuclear quantum effects,\nleading to inaccurate predictions. Here, we present quantum dynamics\nfrom classical trajectories (QDCT), a new protocol to recover the\nquantum wavepacket from the classical trajectories generated by surface\nhopping. In this first QDCT implementation, we apply it to recover\nresults at the multiple spawning level from postprocessing surface\nhopping precomputed trajectories. With a series of examples, we demonstrate\nQDCT’s potential to improve the accuracy of the dynamics, correct\ndecoherence effects, and diagnose problems or increase confidence\nin surface hopping results. All that comes at virtually no computational\ncost since no new electronic calculation is required.