Through a variety of highly correlated methods combined with large basis sets we have studied the electronic structure of FeO, FeO(+), and FeO(-). In particular, we have constructed complete potential energy curves for 48, 24, and 4 states for the FeO, FeO(+), and FeO(-) species, respectively, at the multireference level of theory. For all states examined we report energetics, common spectroscopic parameters, and dipole moments. Overall our results are in good agreement with experiment, but we have encountered as well interesting differences between experiment and theory deserving further investigation.

We present a high level ab initio study of NiO and its ions, NiO(+) and NiO(-). Employing variational multireference configuration interaction (MRCI) and single reference coupled-cluster methods combined with basis sets of quintuple quality, 54, 20, and 10 bound states of NiO, NiO(+), and NiO(-) have been studied. For all these states, complete potential energy curves have been constructed at the MRCI level of theory; in addition, for the ground states of the three species core subvalence (3s(2)3p(6)∕(Ni)) and scalar relativistic effects have been taken into account. We report energetics, spectroscopic parameters, dipole moments, and spin-orbit coupling constants. The agreement with experiment is in the case of NiO good, but certain discrepancies that need further investigation have arisen in the case of the anion whose ground state remains computationally a tantalizing matter. The cation is experimentally almost entirely unexplored, therefore, the study of many states shall prove valuable to further investigators. The ground state symmetry, bond distances, and binding energies of NiO and NiO(+) are (existing experimental values in parenthesis), X(3)Σ(-)(X(3)Σ(-)), r(e) = 1.606 (1.62712) Å, D(0) = 88.5 (89.2 ± 0.7) kcal/mol, and X(4)Σ(-)(?), r(e) = 1.60(?) Å, D(0) = 55 (62.4 ± 2.4) kcal/mol, respectively. The ground state of NiO(-) is (4)Σ(-) (but (2)Π experimentally) with D(0) = 85-87 (89.2 ± 0.7) kcal/mol.

We present a systematic and high-level ab initio study of CoO and its ions, CoO(+) and CoO(-). Employing variational multireference (MRCI) and single-reference coupled-cluster methods combined with basis sets of quintuple quality, we have calculated 50, 31, and 7 bound states for CoO, CoO(+), and CoO(-), respectively. For all these states, complete potential energy curves have been constructed at the MRCI level of theory, whereas for a few low-lying states core subvalence and scalar relativistic effects have been taken into account. We report energetics, spectroscopic parameters, dipole moments, and spin-orbit coupling constants. The ground states of CoO, CoO(+), and CoO(-) are X(4)Δ, X(5)Δ, and X(5)Δ, respectively, the latter established for the first time. The CoO is quite ionic with a Co to O Mulliken charge transfer of ~0.6 electrons and a dipole moment μ(X(4)Δ) = 4.5 ± 0.1 D. The overall agreement between theory and experiment is good, but there are also important deviations. Despite the seeming simplicity of these diatomic species, reliable results can only be obtained at a high level of theory.

The species ZnO and ZnO(+/-) have been studied by variational multireference and coupled-cluster [RCCSD(T)] methods employing augmented basis sets of quintuple cardinality. Full potential energy curves are reported for 13, 10, and 2 bound states of ZnO, ZnO(+), and ZnO(-), respectively. All our results are in excellent agreement with existing experimental findings.

The electronic structure of the diatomic species CoH, CoH(+), and CoH(-) have been studied mainly by multireference configuration interaction (MRCI) methods and basis sets of quintuple quality. The restricted coupled-cluster with iterative singles + doubles + quasi-perturbative connected triples, RCCSD(T), approach was also employed, limited however to the ground states only. At the MRCI level we have constructed 27 (CoH), 24 (CoH(+)), and 12 (CoH(-)) potential energy curves correlating adiabatically to six, seven, and two energy channels, respectively. For the ground states scalar relativistic and core-subvalence effects have been taken into account. We report energetics, spectroscopic parameters, dipole moments, excitation energies, and spin-orbit coupling constants. Our CoH calculated results are in accord with experiment, but there is an interesting discrepancy between theory and experiment concerning the dipole moment, the former being significantly larger than the latter. Experimental results on CoH(+) and CoH(-) are scarce. The ground state of CoH, CoH(+), and CoH(-) are definitely of (3)Φ, (4)Φ, and (4)Φ symmetries with calculated (experimental) dissociation energies D(0)(0) = 46.4 ± 0.5(45.0 ± 1.2), 49.6(47 ± 2), and 45.6(43.1 ± 1.2) kcal/mol, respectively. In all 24 calculated CoH states, a Co-to-H charge transfer of 0.2-0.3 e(-) is recorded; in CoH(-), however, the negative charge resides almost exclusively on the Co atom.