VNFDOPRO 1 In the long range, all the spin-splitting potentials are in somewhat good agreement. It can be speculated that both the lack of size consistency and the internal contraction error in the configuration interaction calculations lead to the discrepancy in the MRCI-F12+Q/augcc-pVTZ-F12 potential, and it is seen that the spin-splitting approach resolves the issue when the singlet-triplet gap is calculated using the same multireference method. In the shorter range, the potentials computed with the pure CASPT2-F12/aug-cc-pVTZ-F12 calculation and the spin-splitting approach with CASPT2-F12/aug-cc-pVTZ-F12 singlet-triplet gaps do not significantly differ. Similarly, the use of the spin-splitting approach with MRCI-F12+Q/aug-cc-pVTZ-F12 singlet-triplet gaps shows much closer agreement with the pure MRCI-F12+Q/aug-cc-pVTZ-F12 potential, which is likely to be the more accurate of the two multireference approaches at shorter fragment separations. The average of the two spin-splitting approaches is likely to be most accurate overall in the transition state region.