Although it can be tempting to jump right into nonadiabatic molecular dynamics simulations (which are discussed in Section 2.2.2), those simulations can be quite expensive because energy conservation typically requires time steps ∆t = 0.5-1.0 fs, and accurate integration of the couplings (which vary rapidly in regions where energy gaps are small) may require even smaller time steps. Moreover, the results of such simulations are generally meaningful only in the aggregate, i.e., when averaged over an ensemble of trajectories. It may therefore be useful to first locate critical points on the potential energy surface, such as excited-state local minima and MECPs between electronic states, the latter of which not only indicate photochemical funnels are found in coordinate space, but also which vibrational modes provide the strongest coupling between the electronic states in question. Examples of MECP optimization are presented in Section 2.2.1.