DFT study of the role of point and complex defects on luminescence, electronic, and thermodynamic properties of LiF: Mg

Abstract

Thermoluminescence properties of the most widely used thermoluminescence dosimeter, namely LiF: Mg, Ti, are controlled by the concentration of the Mg dopant. The origin of the thermoluminescence peaks and the optical absorption peaks of irradiated LiF: Mg is still not fully understood. In this work, the role of point and complex, intrinsic and extrinsic defects on the electronic structure and thermodynamics of LiF: Mg has been investigated by DFT. The calculations show that the defect complex formed by an Mg impurity with an adjacent F vacancy capturing two electrons, which forms a Z2 center, cannot contribute to thermoluminescence or to luminescence in general. The reason is an induced Stark effect that shifts the defect states into either valence or conduction bands. These findings suggest that to maximize the thermoluminescence response, it would be important to maximize the number of Mg atoms isolated from F vacancies.