Because this difference is only caused by the way the contraction with the pseudo-density matrix is performed, the numerical value of d αβ obtained with a development version of OpenMolcas seems to be equivalent to that of BAGEL. Although the complete derivative coupling has been implemented, the interstate coupling vector h αβ is used for MECI searches because d αβ is singular and undefined at CI points (∆E αβ = 0). Moreover, the CSF contribution CSF d αβ is translationally and rotationally non-invariant, so using the derivative coupling is unsuitable, or at least not helpful, to locate MECIs.