The next example is a PES cut for rotation around the C12-C13 axis shown in the lower panel of Figure . Again, the red dots represent the energies obtained from the PES for the unrelaxed torsional geometries, while the blue line is a fit to the DFT-calculated energies using a function of the form a 0 + a 2 (θ dh -π) 2 + a 4 (θ dh -π) 4 + a 6 (θ dh -π) + a 8 (θ dh -π) 8 + a 10 (θ dh -π) 10 + a 12 (θ dh -π) . The angle of rotation is the dihedral angle between the plane containing C11, C12, and C13 and the plane containing C12, C13, and C24. Labels identify the GM, a local minimum (LM), a transition state (TS1) between the GM and LM and a higher transition state (TS2), above which there is free rotation.