Once we have an in depth description of the states total energies, the next step is to explore how the relative energy depends on the orbitals choice. Figure shows the electron affinity dependence with both the metal and ligand weights at the CASCI and NEVPT2 levels of theory. The huge energy variation at the CASCI level indicates the large difference between optimal sets of orbitals for each state and, consequently, between their wave functions. That way, the closer to (m, w) = (0, 0), the lower is the S 2+ state total energy and the higher the S + one. However, the smaller is the d -occupancy mixing of the former. Moreover, due to the orbitals being closer to the optimal for a d 9 -occupancy, the S + state energy is over-corrected at the NEVPT2 level of theory. This provokes an inverted behavior in how the electron affinity depends with the weights. Figure : S 2+ electron affinity calculated using our proposed step-wise protocol. Each point corresponds to a set of (m, w) coordinates, where m is the weight assigned to the metal orbitals optimization and w the one assigned to the molecule states. Both vary from 0 to 100% in increments of 10%, the latter is marked in the x-axis and the former is represented by the full lines, where the increase direction is represented by the arrows. In orange diamond points are those at the CASCI level of theory and in black triangles those from NEVPT2.