Ground and low-lying states of FeH+ as derived from a b i n i t i o self-consistent field and configuration interaction calculations

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The electronic states of FeH+ dissociating into Fe+ (6D) and H (2S) have been studied at the restricted open Hartree–Fock (ROHF) and configuration interaction (CI) level of theory, using a pseudopotential approach and considering or not relativistic effects. The ground state appears to be a 5Δ at the ROHF level but inclusion of correlation effects leads to a 5Π ground state. Nevertheless both states exhibit in all cases a near degeneracy. The calculated D0 is about 90% of the experimental value at the CI level whereas ROHF calculations account only for about 25% of the experimental dissociation energy.