Structural and electronic properties of SrAl₂O ₄:Eu²⁺ from density functional theory calculations

A stoichiometric micro-sized powder SrAl₂O₄:Eu ²⁺ was synthesized by traditional solid state reaction at 1250 C. Low-temperature spectroscopic measurements revealed two luminescence bands at 450 nm and 512 nm; their origin was discussed. Theoretical calculations of the structural and optical properties of SrAl₂O₄:Eu ²⁺ in the framework of the density functional theory (DFT) were carried out; the obtained results were compared with the corresponding experimental data. For the first time, the position of the lowest 4f states of Eu in the host's band gap was calculated for both available Sr positions to be at about 4.5-5 eV above the top of the valence band. Reliability of this result is confirmed by good agreement with the experimental value of the O(2p)-Eu(4f) charge transfer energy, which is equal to about 4.9 eV.