Local characteristics of the electronic structure of molecular systems predicted by the unrestricted Hartree-Fock method

The formalism underlying the calculations of local characteristics of the electronic structure of molecules and crystals by ab initio quantum-chemical methods was considered. Formulas for the bond order and the covalence and full valence of atoms in molecules and crystals were derived within the framework of the restricted and unrestricted Hartree-Fock methods. The correctness of the proposed approach was demonstrated by the Hartree-Fock and CAS SCF calculations of the electronic structure of the Ti₂O₃ crystal (by using the band and cluster models).