In this example, fulvene serves as a photoactive molecule undergoing structural transformation during nonadiabatic dynamics simulations initiated from the first excited state. Fulvene is adopted here because it is a typical test molecule used for the development of methods and benchmarks in NAMD. The reason for its popularity stems from its small size (allowing quick simulations even at fully correlated levels) and ultrafast dynamics (all relevant events are completed in less than 100 fs).