Step 4: The two active points from Step 3, located at -120 • and 120 • , spawn four new constrained optimizations. Since the dihedral grid is periodic, the "leftward" optimization from -120 • wraps around to the "right-most" grid point at 180 • . The "rightward" optimization from +120 • also targets this grid point. The result of the two new optimizations is compared, and the one with the lowest energy is assigned as the new data for the grid point at 180 • , which is assigned as active (red) in the current step. In this example, the optimization from -120 • to -60 • results in a equal-or higher-energy geometry similar as before. However, the optimization from 120 • to 60 • results in a lower-energy geometry, due to finding a lower-energy local minimum. To explore the potential energy surface around this new lowest-energy local minimum, the 60 • grid point is set as an active point.