Main and Satellite Features in the Ni 2p XPS of NiO

Abstract

The origin and assignment of the complex main and satellite X-ray photoelectron spectroscopy (XPS) features of the cations in ionic compounds have been the subject of extensive theoretical studies using different methods. There is agreement that within a molecular orbital model, one needs to take into account different types of configurations. Specifically, those where a core electron is removed, but no other configuration changes are made and those where in addition to ionization, there are also shake or charge-transfer changes to the ionic configuration. However, there are strong disagreements about the assignment of XPS features to these configurations. The present work is directed toward resolving the origin of main and satellite features for the Ni 2p XPS of NiO based on ab initio molecular orbital wave functions (WFs) for a cluster model of NiO. A major problem in earlier ab initio XPS studies of ionic compounds has been the use of a common set of orbitals that was not able to properly describe all the ionic configurations that contribute to the full XPS spectra. This is resolved in the present work by using orbitals that are optimized for averages of the occupations of the different configurations that contribute to the XPS. The approach of using state-averaged (SA) orbitals is validated through comparisons between different averages and through use of higher order excitations in the WFs for the ionic states. It represents a major extension of our earlier work on the main and satellite features of the Fe 2p XPS of Fe2O3 and proves the reliability and the generality of the assignments of the character and origin of the different features of the XPS obtained with orbitals optimized for SAs. These molecular orbital methods permit the characterization of the ionic states in terms of the importance of shake excitations and of the coupling of ionization of 2p1/2 and 2p3/2 spin–orbit split sub shells. The work lays the foundation for definitive assignments of the character of main and satellite XPS features and points to their origin in the electronic structure of the material.

Self‐Propelled Magnetic Dendrite‐Shaped Microrobots for Photodynamic Prostate Cancer Therapy

“…Two peaks at binding energies of ∼711 eV for Fe 2 p 3/2 and ∼724 eV for Fe 2 p 1/2 with the corresponding satellite peaks at ∼719 and ∼733 eV binding energies can be distinguished. These are characteristics of Fe 3+ ions in hematite [33] . The high‐resolution O 1s spectrum in Figure 1E shows two contributions at ∼532 eV and ∼530 eV binding energy, assigned to Fe−O within Fe 2 O 3 , and hydroxyl groups attached to FeO, respectively.…”

Electrochemical Assembly of Nickel Metal Organic Framework-Decorated Nanoimprinted Gold Dendrites as Peroxidase Mimic for High-Performance Hydrogen Peroxide Sensing

“…The hypothesized structure in Scheme also indicates that the Ni metal center exists as Ni 2+ . The difference between the core level Ni peaks (17.5 eV) and the satellite peaks (18.48 eV) remained comparable. , Further, the sample was examined for the presence of C 1s (Figure C­(a,b)) and N 1s (Figure D) peaks. The peaks at 284.18 and 287.69 eV correspond to CC and C–N bonds, respectively, which are testament for the presence of these elements in the imidazole backbone of the Ni-MOF, as shown in (Figure C­(ii),a,b).…”

CeO2/CuO/NiO hybrid nanostructures loaded on N-doped reduced graphene oxide nanosheets as an efficient electrocatalyst for water oxidation and non-enzymatic glucose detection

“…61,64 The Ni 2p 3/2 satellites appear at 852.0 and 860.0 eV, while the Ni 2p 1/2 satellite is seen at 877.0 eV. 65 The core-level XPS spectrum of N 1s (Fig. 2e) shows a signal at around 399.0 eV, which splits into four peaks.…”