ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

Computational analysis of Cs₂TlInY₆ (Y = Cl, Br, I) halide double perovskites: insights from TB-mBJ and Hartree–Fock (HF) calculations for energy-related properties

Asad Ullah, Sohail Ahmad, Muhammad Sanaullah Shah, Muhammad Yar Khan, Muhammad Sami Rashad, Muhammad Zakria, Yang Mu, Xie Fei, and Hou Ruoxian

Department of Physics, Qilu Institute of Technology, Jinan, People’s Republic of China

E-mail: Dr.asadullahphy@qlit.edu.cn

Received: 30 December 2025  Accepted: 20 April 2026

Abstract:

First-principles calculations were performed using the WIEN2k package to find out the physical characteristics and structural stability of Cs-based halide double perovskites Cs₂TlInY₆ (where Y = Br, Cl, and I) within the context of density functional theory (DFT) and ab-initio molecular dynamics (AIMD). These compounds exhibit structural stability, as indicated by their negative values of formation and ground state energies. The electronic band structure reveals that Cs₂TlInY₆ (Y = Cl, Br and I) exhibits semiconducting behavior with indirect band gaps of 3.52 eV, 2.46 eV, and 1.31 eV, respectively. These band gaps were computed via a modified Becke-Johnson approximation methodology, while the corresponding values via Hartree–Fock (HF) are 4.70 eV, 3.21 eV, and 2.67 eV, which is known for its improved accuracy in band gap analysis. The compounds exhibit strong optical conductivity and maximum output in the visible spectrum of solar energy, alongside peak absorption for all materials, although reflectivity is reduced in this region, it renders them appropriate for optoelectronic and solar cell applications. All compounds exhibit mechanical and dynamic stability with a brittle characteristic; moreover, the covalent bonding nature is supported by Cauchy pressure, which yields negative values. Additionally, the thermoelectric properties of these compounds were analyzed to evaluate their potential for thermoelectric applications. The double perovskites exhibit favorable power factors, Seebeck coefficients, and electronic figures-of-merit, indicating their promise as p-type thermoelectric materials for further investigation.

Graphical abstract

Keywords: Wien2k package; HF; Thermoelectric; Optoelectronics; AIMD theory

Full paper is available at www.springerlink.com.

DOI: 10.1007/s11696-026-04935-x

Chemical Papers 80 (8) 9045–9060 (2026)