In CAHF/CASCI-SO strategy , at first the CAHF method is used to generate the set of φ a molecular orbitals which minimizes the average-energy functional represented on the basis of all possible Slater determinants, of any M S quantum number, built up allowing n el a active electrons to be distributed in all the possible ways in N a active orbitals. Then, in the CASCI-SO step, the CAHF orbitals are used to construct the representation of the total Hamiltonian of the system, which includes both the Born-Oppenheimer electrostatic and spin-orbit Hamiltonian, still on the basis of all possible Slater determinants in the CAS space of n el a electrons in N a orbitals. Finally, the total Hamiltonian is diagonalized to obtain the energy levels.