First-principles study of luminescence in Eu2+-doped inorganic scintillators

Luminescence in Eu2+ activated materials corresponds to a transition from an excited state where the lowest Eu 5d level is filled with one electron [often called the (Eu2+)* state] to the ground state with a half-filled 4f shell with seven electrons of the same spin. We have performed theoretical calculations based on density functional theory to determine the ground state band structure of Eu-doped materials as well as study the (Eu2+)* excited state. Calculations were performed on Eu-doped materials, experimentally known to be either scintillators or nonscintillators, in order to relate theoretically calculable parameters to experimentally observed properties. Applying criteria previously developed for Ce-doped systems [A. Canning, A. Chaudhry, R. Boutchko, and N. Gronbech-Jensen, Phys. Rev. B 83, 125115 (2011)] to new Eu-doped materials, we developed a list of candidate materials for new bright Eu-activated scintillators. Ba2CsBr5:Eu is an example of a new bright scintillator from our candidate list that has been synthesized in microcrystalline powder form. As discussed in our previous paper on Ce-doped materials, this approach was designed as a systematic high-throughput method to aid in the discovery of new bright scintillator materials by prioritization and down-selection on the large number of potential new materials.