An algebraic method for solving Hartree-Fock equations. II. Open-shell molecular systems

This paper is the follow-up of an earlier one. It presents (i) the system of nonlinear algebraic equations of the Algebraic Method corresponding to the Hartree-Fock-Pople-Nesbet Approach; and (ii) a systematic study of the variations of the energy of an Unrestricted-Hartree-Fock (UHF) type wave-function as a function of molecular orbitals, for some molecular systems. The results show explicitly for NH, OH and CH the existence of two Hartree-Fock (HF) minimum points with the same spatial symmetry and satisfying the aufbau occupancy rule