We used the wavefront propagation algorithm implemented in TorsionDrive , an open source package, to generated QM surfaces of motors S, N and O (Figure ). TorsionDrive runs geometry optimizations constrained at each grid point multiple times, from different propagating directions, to find the lowest energy structure at that point. TorsionDrive also benefits from using multiple starting structures to seed the propagation; the seed structures we used were the final metastable form structures from QM surface-hopping MD, plus the structures shown in Fig 1 . Relative to less exhaustive scanning methods in the literature, such strategy is less sensitive to convergence failures at some grid points, to hysteresis (i.e. different results when the same point is scanned from different direction), and to optimizations being trapped in local minima rather than the lowest energy structure at the grid point. As shown previously , these problems can be particularly severe for alkene motors, likely due to nontrivial size (48 atoms for Motor S) and high rotation barriers, but problems are largely alleviated by the TorsionDrive method. Energies and gradients were computed by the Psi4 package for use in TorsionDrive.