Ground States, Configurations, and Truncated Orbital Bases of the Iron-Series Atoms

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Abstract
This article presents an analysis of several related topics of importance to the orbital theory of electronic states of transition‐metal atoms in the framework of the Hartree–Fock approximation. First, it is shown that the principle experimental features of the term separations for these atoms are determined primarily by the Hartree–Fock wavefunction. Within the framework of this one‐particle description, it is then demonstrated that subtle competing electrostatic effects are responsible for the well‐known inversions of ground‐state configurations. Beyond the one‐particle description, electron correlation contributions, determined as differences between experimental and Hartree–Fock term separations, are demonstrated to have remarkably systematic trends that enable predictions to be made of term values of stable but unobserved excited states of the ions. Finally, useful small bases that maintain the principal features of the Hartree–Fock description for reliable exploratory SCF calculations on these atoms and their molecules are presented and discussed.