Within the FAIMP approach, the crystal field levels and magnetic proprieties are estimated from the wave function of the metal y M m , optimized at CAHF/CASCI-SO level in presence of the ligands described by FAIMP model as: Within the NOGF theory presented in this paper, the crystal field levels and magnetic proprieties are estimated by variational optimization of the pure electrostatic Hamiltonian on the basis of the product functions in eq. ( ), which includes (i) the wave functions of the isolated metal y M m optimized at CAHF/CASCI-SO level, (ii) the ground state closed shell single Slater determinants optimized at HF level describing the ligands as: