The calculation of the dipole moments of NiH, TiO, and FeO

Abstract

We explore several computational strategies for computing the dipole moment of theX2Δ state of NiH, theX3Δ state of TiO, and theX5Δ state of FeO. The averaged coupled-pair functional (ACPF) method gives consistently the best agreement with experiment, but can become intractable, as rather large zeroth-order reference spaces can be required. At the ACPF level, unlike the multireference configuration-interaction (MRCI) level, the dipole moments determined as an expectation value and by finite-field methods are similar, and are insensitive to natural orbital iteration. Our best theoretical results for NiH are in excellent agreement with experiment, whereas our best dipole moments for TiO and FeO are both about 10%–15% larger than the recently measured values.