The TPSSh-D3 functional is included since the adiabatic energy difference was closest to the XMS-CASPT2 and RASPT2 values. On the other hand, PBE0-D3 and PBE-D3 are included since ∆E S 0 -T 0 was the most negative and most positive, respectively, of the tested functionals. Scans with M06-L and TPSS-D3 are included as supporting information (Fig-