Structure and optical properties of high light output halide scintillators

TL;DR

This study uses first principles calculations to analyze the structural and optical properties of various high light output halide scintillators, revealing their isotropic optical behavior and improved band gap predictions with the Tran-Blaha functional.

Contribution

It provides detailed computational insights into the optical properties of halide scintillators, highlighting the effectiveness of the Tran-Blaha functional for accurate predictions.

Findings

Most halide scintillators are highly isotropic optically.

Tran-Blaha functional significantly improves band gap predictions.

Implications for developing ceramic halide scintillators are discussed.

Abstract

Structural and optical properties of several high light output halide scintillators and closely related materials are presented based on first principles calculations. The optical properties are based on the Engel-Vosko generalized gradient approximation and the recently developed density functional of Tran and Blaha. The materials investigated are BaBr$_2$, BaIBr, BaCl$_2$, BaF$_2$, BaI$_2$, BiI$_3$, CaI$_2$, Cs$_2LiYCl$_6$, CsBa$_2$Br$_5$, CsBa$_2$I$_5$, K$_2$LaBr$_5$, K$_2$LaCl$_5$,K$_2$LaI$_5$, LaBr$_3$, LaCl$_3$, SrBr$_2$, and YI$_3$. For comparison results are presented for the oxide CdWO$_4$. We find that the Tran Blaha functional gives greatly improved band gaps and optical properties in this class of materials. Furthermore, we find that unlike CdWO$_4$, most of these halides are highly isotropic from an optical point of view even though in many cases the crystal structures and other properties are not. This general result is rationalized in terms of halide chemistry. Implications for the development of ceramic halide scintillators are discussed.