Electronic and optical properties and upper light yield estimation of new scintillating material TlMgCl3: Ab initio study

Based on the density functional theory, this work reports an Ab initio investigation on the electronic and optical properties as well as the upper light yield estimation of the new scintillating material TlMgCl3. The DFT calculations are performed with the help of the FP-LAPW method using GGA and GGA + mBJ approximations as well to ensure a reliable band gap and accurate electronic band structure and optical properties. The computed band structure and density of states indicate that, this material has a direct band gap of 6.04 eV at M point. By including the spin–orbit coupling (GGA + mBJ + SOC), a similar direct band gap is obtained but with a value equals to 5.74 eV, due to the splitting of Tl 6p states at the bottom of the conduction band. Moreover, this coupling changes the conduction band and creates a very small gap and dips which enhance the intra-band radiative transitions. Additionally, the imaginary part of the dielectric function, reflectivity, absorption coefficient, and the refractive index along × and z directions are calculated and discussed in the two cases: GGA + mBJ and GGA + mBJ + SOC. Precisely, the obtained results demonstrate that, this material has a high rate of transmittance greater than 92.5% in the emission range. Besides this, the upper light yield (LYsc) in the ideal conditions, with a limit of 100%, is estimated in these two cases to be 66,225 ph/MeV and 69,686 ph/MeV, respectively. These findings contribute to explain the reason behind the excellent scintillation properties of TlMgCl3 and make this material a good candidate for scintillation detectors applications