Defect Structures, Electronic Properties, UV-Vis, and EPR Parameters for Rh2+ Centers in LiD: A DFT Study

The defect structures and electronic properties of orthorhombic elongated (O-E) and tetragonal compressed (T-C) Rh2+ centers in LiD are theoretically studied using Density Functional Theory (DFT) with the periodic CP2K program. The calculations demonstrate obvious differences in defect structure between the two centers. O-E center with one next nearest neighbor (nnn) cation vacancy (V-Li) in [100] axis shows the Jahn-Teller elongation of about 0.076 angstrom along [001] axis, whereas T-C center with one nnn V-Li in [001] axis exhibits a compression of about 0.049 angstrom along this direction. The ligand between the central Rh2+ and the V-Li is found to move away from the V-Li by about 0.038 or 0.035 angstrom for O-E or T-C center. The larger magnitude of the overlap population (approximate to-0.5907 or -0.5494 e) of the RhD bonds in O-E or T-C center than that (approximate to 0.2373 e) of the host LiD bonds in pure LiD indicates much stronger covalency of the former. The simulated UV-Vis and electron paramagnetic resonance (EPR) spectra with the embedded cluster model in ORCA code are consistent with the experimental data. The present results are discussed and compared with those of the previous perturbation calculations.