MnO+: a challenge for density functional theory methods

Abstract.

 The ⁵Σ⁺ and ⁵Π states of MnO⁺ are studied using density functional theory (DFT) and the complete-active-space self-consistent-field (CASSCF)/multireference configuration interaction (MRCI) and CASSCF/average coupled pair functional (ACPF) levels of theory. All the DFT methods give a reasonable description of the ⁵Σ⁺ state, but only the hybrid functionals give ⁵Π spectroscopic constants that agree with those obtained using the MRCI and ACPF approaches. The origin of the difference between the pure and hybrid functionals is discussed.