The geometry relaxation component to the total correction is gauged using the difference between relaxed and rigid CASPT2/cc-pVDZ potentials along the D 3d MEP), as shown in Figure as a function of the radical-radical separation distance, R CC . These corrections are very small due to the strongly non-planar C 3v geometry of CF 3 requiring minimal rearrangement as the radicals approach each other. In contrast, with the analogous hydrocarbon reaction 2 CH 3 --→ ←--C 2 H 6 there is a large rearrangement and geometry relaxation effect arising from the transition from the planar geometry of CH 3 to the sp 3 -hybridization in C 2 H 6 .