First-principle investigation of Jahn–Teller distortion and topological analysis of chemical bonds in LiNiO2

First-principle GGA+U calculations were performed on the undistorted rhombohedral R3̄m model, the collinear Jahn–Teller distorted monoclinic C2/m model, and six non-collinear Jahn–Teller distortion ordering models of LiNiO2. The zigzag and C2/m models are found to be the most stable and the next most stable structural models, respectively. An energy gap appears for the C2/m and zigzag structures, whereas no energy gap appears for the R3̄m structure. Topological analyses were performed on the R3̄m, C2/m and zigzag models using the atoms-in-molecules theory and the electron localization function. The results show that the Ni–O interaction is the transit closed-shell interaction, in which the net electron transfer occurs from the Ni ion to the ligand O ions. The Ni–O bond possesses the σ dative bond character and is polarized toward the O ions. In the distorted structures, the bonding electrons around the oxygen atom are strongly polarized toward the long Ni–O bond.