Electronic transitions in layered hydroxides: Consequences of trigonal distortion of octahedral symmetry

This work describes the assignment of the electronic spectra of metal ions in D_3d coordination symmetry. Layered hydroxides are a class of materials that host transition metal ions such as Ni²⁺, Co²⁺, and Cr³⁺ in D_3d coordination symmetry. The electronic spectra of these ions in the layered hydroxides exhibit significant fine structure which is assigned to transitions arising from D_3d coordination symmetry. Towards this end, the correlation diagrams- complete or partial, and the resultant Tanabe-Sugano like diagrams for D_3d symmetry are obtained from first principles and supported by DFT based computations. The approach engendered here helps in better understanding of the electronic transitions arising due to lower symmetry.