APS -APS March Meeting 2017 - Event - First-principles Investigation of the Structure, Mobility and Optical Properties of Self-Trapped Excitons in Alkali Metal, Lanthanum and Barium Halide Scintillators

摘要

The performance of new and improved materials for gamma ray scintillator detectors is dependant onmultiple factors such as quantum efficiency, energy transport etc.In halide scintillator materials the energy transport is often impacted byself-trapped exciton (STE) formation and mobility.We present first-principles calculations at the hybrid density functional theorylevel for the structure, mobility and optical properties of STEs and their associated latticedefects ($V_K$ centers) in two important families of scintillator materials, alkali metal andlanthanum halides (AX and LaX).AX and LaX have been extensively characterized by experiments and serve as benchmark systemsto assess the accuracy of our theoretical procedure. We show that hydrid functionals accurately predict the different types of self-trapped excitons (on and off-center)found in AX and LX materials in agreement with EPR experiments.We then applied this approach to perform preliminary studies onclasses of new scintillator materials including the barium mixed halidesand compared with our new experimental results.These studies have the potential to benefit the development of improved scintillatormaterials tailored for specific applications.