FP-LAPW investigation on structural, electronic and optical properties of Eu2+-doped MF2 (M = Ca and Ba)

The structural, electronic and optical properties of MF2 (M = Ca and Ba) doped with Eu2+ ion have been studied using full-potential linearized augmented plane wave (FP-LAPW) method based on the density functional theory (DFT), as implemented in Wien2k package. Due to the difference in ionic size, the Eu2+ incorporation in MF2 induces a re-accommodation of its nearest neighbors to reach more stable configuration. Along with the generalized gradient approximation (GGA-PBE), the electronic properties also are investigated by Tran-Blaha modified Becke Johnson potenital (mBJ) due to that it gives very accurate band gap of a lot of types of solid. The Eu2+ doping causes a slight increase on band gap of CaF2 and BaF2, and there is found Eu2+-4f state in the forbidden energy region of host. In this work, the spin-orbit coupling (SOC) effect on electronic properties of MF2:Eu2+ is also investigated. Finally, the doping effect on optical absorption property is also studied by deriving the absorption coefficient of all materials on consideration from their calculated complex dielectric function in energy range up to 17 eV.