DFT studies of the role of anion variation in physical properties of Cs2NaTlBr6-xClx (x = 0, 1, 2, 3, 4, 5, and 6) mixed halide double perovskites for optoelectronics

Halide-double perovskites have various benefits over lead-based perovskites due to their suitable optical absorption efficiency, higher stability, tunable bandgap, large carrier mobility, easy availability, and low cost. The structural, electrical, optical, and mechanical characteristics of the lead-free halide double perovskites Cs2NaTlBr6-xClx (x = 0, 1, 2, 3, 4, 5, and 6) are investigated by utilizing the first-principles density functional theory (DFT). The structural properties were computed at equilibrium, revealing that the crystals undergo structural phase transitions as the doping concentration varies. However, crystal stability was confirmed through the evaluation of the tolerance factor. The HSE06 functional is used to correct the bandgap underestimation by GGA-PBE. The band edge profile and electron density of states confirm the direct-bandgap semiconducting nature of the compounds. The bandgap increases approximately linearly with Cl incorporation, sharply tuned from 0.80–1..., , , # DFT Studies of the Role of Anion Variation in Physical Properties of Cs2NaTlBr6-xClx (x = 0, 1, 2, 3, 4, 5, and 6) Mixed Halide Double Perovskites for Optoelectronics

Dataset DOI: [10.5061/dryad.8gtht770d](10.5061/dryad.8gtht770d)

## Description of the data and file structure

We conducted the theoretical and simulation study of mixed halide double perovskites Cs2NaTlBr6-xClx based on the density functional theory. We investigated the structural, mechanical, and thermodynamic stability of the considered materials and electronic and optical properties to determine the material's potential as a candidate for optoelectronics. In HBD_Mixed_anions.zip, the different data types folder is for two pure double perovskites, such as Cs₂NaTlCl₆ & Cs₂NaTlBr₆. Further, the Cl2Br4, Cl4Br2 (x = 2, 4) in ClxBr6-xData33 and ClBr5, Cl3Br3, Cl5Br (x= 1, 3, 5) in ClxBr1-xpart4 files are arranged for Cs2NaTlBr6-xClx mixed halide double perovskites. In each of the folders, readers will find the dataset fo...,