The interrelation between theoretically determined vertical ionization potentials in transition metal compounds based on the ∆SCF approximation (Iv,j∆SCF) and based on the “transition operator (TO)” method (Iv,jTO) has been investigated. Numerical results in the outer valence region have been obtained by means of semiempirical INDO calculations. The difference between the calculated ionization energies (Iv,j∆SCF and Iv,jTO) is enlarged with increasing atomic numbers of the transition metal center due to noncompensating terms in third order of perturbation. The necessary conditions for the imbalance of both theoretical procedures are large two-electron interaction integrals and highly populated transition metal hole-states. Both requirements are enhanced by going from the left side of the 3d series to the extreme right. For d4-d6 complexes a simplified expression for Iv,j∆SCF has been derived containing only one third order element.
The forming factors of high values of superconducting transition temperature Tc in 3d-transition metal compounds V. Particularities of ab initio cluster X_\alpha-discrete variation method (X_\alpha-DVM): exchange spin-spin electron interaction
