To secure that such a mix in the singly occupied orbital, Equation (3), is not an artifact caused by the restriction of the active space, we increased the active space to also include the orbital describe in Equation ( ), but without re-optimization. More specifically, a CAS (39,20), due to the limit of 20 active obitals in the code used. The result was the same single determinant wave function and, consequently, total energy. The only exception is the m = w = 100 % case, were the additional active orbitals fixed the discontinuity of the total energy, whose energy is marked by the grey point in Figure ).