Geometric, electronic and optical properties of undoped and cerium-doped La₅(Si₂₊ₓB₁₋ₓ)(O₁₃₋ₓNₓ) solid solutions: A theoretical investigation

The geometric properties and electronic structures of La₅(Si₂₊ₓB₁₋ₓ)( O₁₃₋ₓNₓ) solid solutions and 4f→5d transitions in Cerium-doped La₅Si₂BO₁₃ phosphors are studied by combining the hybrid density functional theory (DFT) calculations (with the standard PBE0 functional) and the wave function-based embedded cluster ab-initio calculations (with the CASSCF/CASPT2/RASSI–SO methods). The hybrid PBE0 calculations exhibit the site preferences of different atomic pairs and Ce³⁺ ion in hosts, and predict the variation trend of the band gap for the La₅(Si₂₊ₓB₁₋ₓ)(O₁₃₋ₓNₓ) with x varying between 0 and 1.0. The energies and relative oscillator strengths for 4f→5d transitions of Ce³⁺ ions (without and with N³⁻ ion in their local environments) in the La₅Si₂BO₁₃ host are derived from the embedded cluster ab-initio calculations. The experimental spectra of La₅Si₂BO₁₃:Ce³⁺ phosphors are successfully assigned, according to the calculated schematic diagrams of 4f→5d transitions for Ce³⁺ ions in the host. On the basis of the various empirical models of Dorenbos, the energy locations of 4f ground states and the lowest 5d states of all the Ln³⁺ and Ln²⁺ ions in the La₅Si₂BO₁₃ host are further derived from the ab-initio calculated 5d barycenter of Ce³⁺ ions as well as the experimental spectra. Copyright © 2017 Elsevier B.V. All rights reserved.