Starting with the reduced specie (S + ), its Hartree-Fock (HF) wave function results in a d 10occupancy configuration, associated to a Cu + system, that is a formal charge in accordance with the expected chemical intuition. Moreover, when the coupled-cluster wave function with singles and doubles (CCSD) Despite of the good description using optimal molecular orbitals, we can obtain a more complete picture of the electronic structure using our protocol to control the optimization of metal and ligand orbitals separately, and see how they affect the energy. The dependence of the S + ground state total energy (using a single Slater determinant wave function) with the optimization parameters is shown in Figure . We will analyse first the energy dependence with the d -orbital size, that can be controlled with the weight used in the box I in the flowchart of Figure . Such a control of the d -orbital size is possible because there is an almost affine dependence between the weight and the orbital size, as shown in reference in the neutral iron atom case and specifically for the copper case in Figure at the Supporting Information. Thus, using our proposed optimization we can measure the subsystem energy variation from the orbitals having optimal size for a d 10 configuration, of around 0.98 a 0 , to optimal d 9 orbitals, with size of 0.90 a 0 . Figure From scandium to copper neutral atoms, the magnitude of 3d -orbital size variation decreases, whereas this size effect over the relative energy among distinct d -occupancies drastically increases. For instance, this leads to a variation in relative energies of up to 8.7 eV between the neutral copper atomic states with d 9 and d 10 -occupancies and almost 10 eV for the Cu 2+ → Cu + electronic affinity (as shown in Figure ).