First-principles investigation of electronic and optical properties in ternary silver-based halides MlAgmXn

In this study, first-principles calculations were employed to investigate the structural, electronic, and optical properties of the ternary silver-based halides M_lAg_mX_n(M = K, Rb, Cs; X = Cl, Br, I), including M₂AgX₃, MAg₂X₃, and MAgX₂. The results reveal that M₂AgX₃ and MAg₂X₃ exhibit direct band gaps, while MAgX₂ displays an indirect band gap. The band gap can be effectively tuned by varying the X⁻ ions, with M₂AgX₃ showing the largest band gap value among these three structural types. The influence of spin-orbit coupling (SOC) on band gap values was also evaluated, showing systematic variations with both halide composition and crystal structure. In the near-ultraviolet region, absorption increases as X⁻ ions change from Cl⁻ to Br⁻ to I⁻, with MAg₂X₃ halides exhibiting the highest absorption among the three structures. Overall, our theoretical investigation of the M_lAg_mX_n halides offers promising optoelectronic tunability through compositional and structural engineering, highlighting their potential optoelectronic applications.