Theoretical Determination of the Electronic Structures and Energy-Level Splitting for Pr³⁺-Doped Y₂SiO₅ Crystals

Trivalent praseodymium (Pr³⁺)-doped yttrium silicate (Y₂SiO₅) crystals have been widely used in various phosphors owing to their excellent luminescence characteristics. Although a series of studies have been carried out on its application prospects, the electronic structures and energy-transfer mechanisms of Pr³⁺-doped Y₂SiO₅ (Y₂SiO₅:Pr) remain an exploratory topic. Herein, the crystal structure analysis by the particle swarm optimization structure search method is used to study the structural evolution of Y₂SiO₅:Pr. Two novel structures with local [PrO₇]^-11 and [PrO₆]^-9 [Y₂SiO₅:Pr (I) and Y₂SiO₅:Pr (II)] are successfully identified. The impurity Pr³⁺ ions occupy the Y³⁺ sites and successfully integrate into the Y₂SiO₅ host crystal with a Pr³⁺ concentration of 6.25%. The calculated electronic band structures show that the doping of Pr³⁺ induces a reduction in band gaps for the host Y₂SiO₅ crystal. The conduction bands near the Fermi level are completely composed of f states. For the atomic energies of Pr³⁺ in Y₂SiO₅, the Stark levels and transitions are properly simulated based on a new set of crystal field parameters (CFPs) at the C₁ site symmetry. A satisfactory r.m.s. dev. of 15.57 cm^-1 with 9 free ion parameters (plus 27 fixed CFPs as obtained from ab initio calculation) fitted to the 33 observed levels is obtained for the first time. The plentiful energy-level transition lines, from the visible light to the near-infrared region, are deciphered for Pr³⁺ in Y₂SiO₅. Blue ³P₀ → ³H₄ at 465 nm is calculated to be a strong emission line, and it might be an ideal channel for laser actions. These results could not only provide important insights into the rare-earth-doped crystals but also lay the foundation for future research studies of designing the new laser materials.