Exploring Halide‐Induced Modifications in Nontoxic Rb ₃ Te <i>X</i> ( <i>X</i>  = F, Cl, and Br) Antiperovskites for Improved Optoelectronic Functionality

This study presents a comprehensive investigation of the fundamental properties of Rb 3 Te X ( X = F, Cl, and Br) antiperovskite compounds using density functional theory (DFT). A detailed analysis of their structural, electronic, optical, mechanical, and thermal behaviors is conducted to assess their potential in next‐generation material applications. The electronic bandgaps, calculated using the generalized gradient approximation‐Perdew–Berke–Ernzerhof (GGA‐PBE) functional, are found to be 0.424, 1.655, and 1.574 eV for Rb 3 TeF, Rb 3 TeCl, and Rb 3 TeBr, respectively. To achieve greater accuracy, the hybrid HSE06 functional is employed, yielding slightly higher bandgap values of 2.198, 2.173, and 2.164 eV for Rb 3 TeF, Rb 3 TeCl, and Rb 3 TeBr, respectively. The variation in halogen size notably influences the compounds’ crystal structure, including bond lengths and unit cell volumes, and also impacts their mechanical stiffness and thermal stability. All three compounds demonstrate ductile behavior, supported by Poisson’s and Pugh’s ratios exceeding the critical thresholds. Moreover, their electronic bandstructures (EBSs) strongly affect their optical responses, making them promising candidates for optoelectronic technologies. With their balanced electronic, structural, and mechanical characteristics, Rb 3 Te X ( X = F, Cl, and Br) compounds hold significant promise for applications in solar cell absorbers, light‐emitting diodes, and other advanced optoelectronic devices.