Theoretical confirmation of a 4Δ ground state for FeH

Abstract

Large CAS SCF/multireference configuration interaction (MRCI) and modified coupled pair functional (MCPF) calculations are carried out for the 4Δ and 6Δ states of FeH using very large Gaussian basis sets. At the MCPF level, 3s and 3p correlation preferentially lowers the 4Δ state by 0.10 eV. Adding this inner-shell correlation effect to our best CAS SCF/MRCI+Q valence treatment results in a 4Δ- 6Δ separation of 0.16 eV. This supports the interpretation of the photodetachment spectra of Stevens et al. that places the 6Δ state about 0.25 eV above the 4Δ ground state.