(2.2.14) Gidopoulos : To address the recurring question by Vignale in contribution (2.2.12), I would like to point out that the Kohn-Sham orbitals are in fact as "energetically optimal" as the Hartree-Fock ones. Let me first quote Walter Kohn, who said in his Nobel Prize lecture that while, the Hartree-Fock orbitals are "total energy optimal", the Kohn-Sham orbitals are "density optimal" because they yield the exact density.