Cerium Activated Scintillation in Yttrium Halides: First Principles Theory and Prediction

Recently, scintillation has been observed in Ce-doped YI₃, YBr₃, and YCl₃ crystals. In particular, YI₃ has been reported to be among the scintillators with the highest luminosity. In this work, we present a systematic study of scintillation in any of the four YHa₃:Ce materials where Ha = F, Cl, Br, I, using ab initio calculations. Last year, our group demonstrated successful application of a method of gauging scintillation properties of Ce-doped crystals based on first-principle calculations using density functional theory. This method has been developed as an integral component of a High Throughput Scintillator Discovery facility based at the Lawrence Berkeley National Lab. By analyzing the energies and spatial localization of the highest occupied band in the ground state and in the lowest excited state, we are able to make qualitative predictions about the possibility of scintillation in Ce-doped compounds. In this paper we present the details of our theoretical approach in application to yttrium halides and compare them with the available experiments. Our results yield a prediction of Ce-based scintillation for all four materials: YF₃, YCl₃, YBr₃ and YI₃ and are in correspondence with the available experimental data. We believe that our method is the first use of first-principles calculations to predict some of the factors necessary for the activation of Ce³⁺ ions in crystals.