First Principles Calculations for Scintillation in Ce-Doped Y and La Oxyhalides

This work presents the results of first principles electronic structure calculations for Cerium (Ce) doped Yttrium (Y) and Lanthanum (La) oxyhalides performed using the pseudopotential method based on the local density approximation in the density functional theory. The relative position of the Ce 4f and 5d levels in the energy gap of the host are determined from the ground-state density of states for the Ce-doped material. Localization of the excited electron is determined from the calculations of the $({\rm Ce}^{3+})^{\ast}$ excited state. A qualitative prediction of Ce-activated scintillation is made based on these theoretical calculations. Our approach indicates that Ce-doped Y and La oxyhalides show progressively better luminescence as we move down the periodic table from oxyfluorides to oxyiodides. These families of materials have been synthesized and the experimental results agree qualitatively with our calculations.