Theoretical Predictions of Structural, Electronic, and Optical Properties of α and β Phases of In2S3

We present the findings of our study, which employed the full-potential linearized augmented plane wave (FP-LAPW+lo) method, to investigate the structural, electronic, and optical characteristics of indium sulfide In2S3 in its cubic (α) and tetragonal (β) phases. Crystal structure optimizations were performed using the standard generalized gradient approximation and local density approximation for the exchange-correlation functional. The electronic structure and linear optical properties were evaluated using the modified Becke–Johnson (mBJ) potential. Our calculations closely match the experimental values for the structural parameters. The computed band gap reveals that In2S3 exhibits a direct band gap semiconductor behavior in the α phase, while in the β phase, it demonstrates an indirect band gap. These results are in excellent agreement with experimental observations. Additionally, we provide a comprehensive analysis of the calculated optical properties, including the dielectric function and refractive index.