Theoretical Determination of the Electronic Structures and Energy-Level Splitting for Pr 3+ -Doped Y 2 SiO 5 Crystals.

Trivalent praseodymium (Pr 3+ )-doped yttrium silicate (Y 2 SiO 5 ) 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 Pr 3+ -doped Y 2 SiO 5 (Y 2 SiO 5 :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 Y 2 SiO 5 :Pr. Two novel structures with local [PrO 7 ] -11 and [PrO 6 ] -9 [Y 2 SiO 5 :Pr (I) and Y 2 SiO 5 :Pr (II)] are successfully identified. The impurity Pr 3+ ions occupy the Y 3+ sites and successfully integrate into the Y 2 SiO 5 host crystal with a Pr 3+ concentration of 6.25%. The calculated electronic band structures show that the doping of Pr 3+ induces a reduction in band gaps for the host Y 2 SiO 5 crystal. The conduction bands near the Fermi level are completely composed of f states. For the atomic energies of Pr 3+ in Y 2 SiO 5 , the Stark levels and transitions are properly simulated based on a new set of crystal field parameters (CFPs) at the C 1 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 Pr 3+ in Y 2 SiO 5 . Blue 3 P 0 → 3 H 4 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.