Abstract
We investigated, using DFT calculations, the electronic, optical, polaron properties and estimate the upper light yield of
Tl
2
ZrCl
6
material. The DFT calculations were performed with GGA+mBJ and GGA+mBJ+SOC approximations to obtain precise electronic, optical and polaron properties. The calculated results showed that
Tl
2
ZrCl
6
has localized valence and narrow discrete conduction bands with many sharp peaks and low dispersion which reflects the heavier effective mass of electron at CBM, 4.63
m
e
, in comparison with that of hole at VBM, 1.05
m
e
. Indirect band gap energy of 4.30 eV was observed and which is close to the experimental value, 4.22 eV. Additionally, in the emission range, this material exhibited a high transmittance rate of around 90% which is an advantage of the scintillation properties. Following DFT calculations, polaron properties and also the temperature-dependence of polaron mobility and relaxation time were calculated by solving the Feynman polaron model, variationally, with the free-energies minimization. The obtained results showed that
Tl
2
ZrCl
6
has a large electron (hole)-phonon coupling,
α
e
=
8.55
(
α
h
=
4.1
)
, leading to large polaron mass, small relaxation time, high scattering rate and low electron (hole) mobility of 0.13
cm
2
V
-
1
s
-
1
(4.17
cm
2
V
-
1
s
-
1
) at room-temperature. Such low mobility has a positive role only in the initial ionization track by increasing the recombination yield. Moreover, using the polaron and simple phenomenological models, the upper light yield was estimated to be 87,757
p
h
/
M
e
V
and 75,187
p
h
/
M
e
V
. Such findings could have important implications for understanding the scintillation behavior of this material to improve its performance as a potential scintillator for γ- and X-rays detection.