Theoretical investigation for the EPR g factors and the local structure for the two tetragonal Ni3+ centers in ACoO2 (A=H, Li)

Abstract

• SH parameters and local structures are analyzed for ACoO 2 :Ni 3+ ( A = H, Li). • Ligand orbital and spin-orbit coupling contributions are included. • Ligand octahedra experience relative elongations 2.57% (and 1.6%) along C 4 axis. The electron paramagnetic resonance g factors and the local structure for the tetragonal Ni 3+ centers in HCoO 2 and LiCoO 2 are theoretically studied from the perturbation formulas of the g factors for a 3d 7 ion with low spin ( S = 1 / 2) in tetragonally elongated octahedra. In these formulas, the related molecular orbital coefficients are quantitatively determined from the cluster approach in a uniform way. According to the calculations, the ligand octahedra around Ni 3+ are suggested to suffer relative elongation 2.57% (and 1.6%) along the [0 0 1] (or C 4 ) axis for the tetragonal Ni 3+ centers in HCoO 2 (and LiCoO 2 ), due to the Jahn–Teller effect. The calculated g factors based on the above Jahn–Teller elongations are in good agreement with the observed values.