Eur. Phys. J. B (2022) 95: 38
https://doi.org/10.1140/epjb/s10051-022-00288-y

Regular Article - Solid State and Materials

Structural, elastic, electronic and optical properties of the newly synthesized selenides Tl₂CdXSe₄ (X = Ge, Sn)

¹ Laboratory for Developing New Materials and Their Characterizations, Department of Physics, Faculty of Science, University of Ferhat Abbas, Setif 1, 19000, Setif, Algeria
² Physics and Chemistry of Materials Lab, Faculty of Science, Department of Physics, University of M’sila, 28000, M’sila, Algeria
³ Unité de Recherche Matériaux Emergents, University of Ferhat Abbas, Setif 1, 19000, Setif, Algeria
⁴ Department of Physics and Astronomy, College of Science, King Saud University, PO Box 2455, 11451, Riyadh, Saudi Arabia
⁵ Laboratoire de Physique Quantique de la Matière et de Modélisation Mathématique (LPQ3M), Université de Mascara, 29000, Mascara, Algeria
⁶ Engineering Department, American University of Iraq-Sulaimani, PO Box 46001, Sulaimani, Kurdistan, Iraq
⁷ Department of Mechatronics Engineering, Faculty of Engineering and Natural Sciences, Bahcesehir University, Besiktas, 34349, Istanbul, Turkey
⁸ Department of Electronics, University of Ferhat Abbas Setif 1, 19000, Setif, Algeria
⁹ Department of Physics, University of Rajshahi, 6205, Rajshahi, Bangladesh
¹⁰ Physics Department, Faculty of Science, King Khalid University, PO Box 9004, 61413, Abha, Saudi Arabia
¹¹ Physics Department, Faculty of Education, Ain Shams University, PO Box 5101, Heliopolis, Roxy, 11771, Cairo, Egypt

^b a_bouhemadou@yahoo.fr, abdelmadjid_bouhemadou@univ-setif.dz

Received: 23 October 2021
Accepted: 21 January 2022
Published online: 1 March 2022

Abstract

Motivated by the growing demand for new performant semiconducting materials, we investigated in detail the structural, elastic, electronic and optical properties of two newly synthesized compounds, namely Tl₂CdGeSe₄ and Tl₂CdSnSe₄, using density functional theory calculations. The calculations were performed relativistically, including the spin–orbit coupling (SOC). The computed equilibrium structural parameters are in excellent agreement with available measurements. Note that the calculations of all the considered properties were performed with the theoretically obtained equilibrium lattice parameters. The predicted monocrystalline and polycrystalline elastic constants reveal that the studied compounds are soft, ductile, mechanically stable and substantially structurally and elastically anisotropic materials. Our calculations using the Tran-Blaha modified Becke-Johnson potential with the inclusion of SOC show that Tl₂CdGeSe₄ and Tl₂CdSnSe₄ are direct bandgap semiconductors. The inclusion of SOC is found to reduce the fundamental bandgap of Tl₂CdGeSe₄ from 1.123 to 0.981 eV and that of Tl₂CdSnSe₄ from 1.097 to 0.953 eV. The l-decomposed atom-projected densities of states were calculated to identify the contribution of each constituent atom to the electronic states in the energy bands. The upper valence subband predominantly comes from the Se-4p states, while the bottom of the conduction band mainly originates from the Se-4p and Ge-4p/Sn-5p states. The frequency-dependent linear optical parameters, viz., the complex dielectric function, absorption coefficient, refractive index, reflectivity and energy-loss function, were calculated for electromagnetic waves polarized parallel and perpendicular to the c-axis in a wide energy window. An attempt was made to identify the microscopic origin of the peaks and structures observed in the calculated optical spectra.