The smoothness of RASPT2 is investigated using three active spaces for a transoid MECI of butadiene (structure (k) in Ref. 64): CAS(4e,4o), RAS(4e,4o)/(0e,0o)/2, and RAS(4e,4o)/(2e,2o)/1. Plots of the branching space around XMS-CASPT2/RASPT2 MECIs and contour plots of the energy difference around the SA-CASSCF/RASSCF CIs are plotted in Figure . In all entries, the MECIs were located for each individual active space. Although there are small irregularities in a few instances (right panel in CAS(4e,4o) and left panel in RAS(4e,4o)/(2e,2o)/1), the PESs obtained using XMS-CASPT2 and XMS-RASPT2 are generally well behaved. These CIs are identified as a peaked single-path as per the P and B parameters. These results show that it is possible to use RASPT2 to locate minimum energy structures and intersections. However, in practice, it is often difficult to reach a satisfactory SCF convergence.