Charge density measurement and bonding character in LiNiO2

Accurate low-order structure factors of LiNiO2 were measured by quantitative convergent-beam electron diffraction (QCBED), and then transformed into X-ray structure factors with Mott formula. Combining the structure factors measured by electron diffraction with the structure factors from X-ray diffraction measurements, accurate charge density maps based on a multipole model were obtained. The parameters of the bond critical points (BCP) were calculated for topological analyses. It shows that closed-shell interactions exist between Ni and O atoms, and that the Ni–O and Ni–Ni bonds exhibit some covalent character. The calculated d-orbital occupancies show the charge deficiency at eg(eg) orbital and charge surplus at eg(t2g) orbital. The remaining 29.12% population of eg(eg) is also an indication of covalent component in the Ni–O bond. The unusual small κdefv value of the O atom is also discussed.