First principles exploration of NiO and its ions NiO+ and NiO−

Abstract

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.

Fragmentation of [Ni(NO3)3]−: A Study of Nickel–Oxygen Bonding and Oxidation States in Nickel Oxide Fragments

“…In contrast, the combination of a late transition metal, Cu + with O •− (bottom), does not result in metal oxidation due to the low-energy 3d orbitals. agreement with recent high-level calculations on [NiO] + 26. Survey calculations for select complexes using other levels of theory do not change the important conclusions from this study.…”

Pseudopotentials for quantum Monte Carlo studies of transition metal oxides

“…For FeO-NiO, somewhat larger errors were observed for the quantum chemical approaches [60][61][62] (0.9-1.7%) while similar accuracy was maintained in DMC (0.3(1)%). The most challenging dimers overall were the weakly bound CuO and ZnO.…”

“…Over this same range, quantum chemistry 58,59 performs significantly better with MAD's of 4-16 cm −1 . For the mid-row FeO-NiO, DMC performs comparatively well with a MAD of 25(4) cm −1 (49(4) cm −1 for TM) for versus 53-84 cm −1 for quantum chemistry [60][61][62] . Finally, for CuO and ZnO the performance is similar between our DMC work and the available coupled cluster calculations, with absolute deviations of 60(1) cm −1 for CuO (68 cm −1 RCCSD(T) 63 ) and 18(8) cm −1 for ZnO (11 cm −1 RCCSD(T) 64 ).…”

“…Note that prior DMC data is not available for the heavier elements (FeO-ZnO). In addition to displaying DMC results from the present (DMC-TM/DMC-OPT) and prior (DMCprev) studies 20,24,57 , Figure 2 contains reference data from high-level quantum chemical calculations [58][59][60][61][62][63][64] , including multi-reference configuration interaction at the level of singles and doubles excitations (denoted MRCI or MRCI+Q with a Davidson-like correction), and restricted/unrestricted coupled cluster with singles, doubles, and perturbative triples (RCCSD(T)/UCCSD(T)). In the discussion below, the deviation from experiment of these three quantum chemical methods is expressed as a range rather than three separate and individually labeled numbers for brevity.…”

Extending spin‐symmetry projected coupled‐cluster to large model spaces using an iterative null‐space projection technique

“…This particular system is interesting because SUHF does not predict the ground state correctly. The dominant configuration of the MRCI ground state is , where only active electrons are shown . While the broken‐symmetry determinant of SUHF necessarily breaks the spin‐symmetry and most likely the spatial symmetry (as SUHF orbitals are usually localized), the SUHF wave function in total can recover not only the former symmetry but also the latter if the determinant ∣Φ A 〉 has an appropriate structure.…”