Electronic, structural, optical and thermoelectric properties of potassium chalcohalide antiperovskites from first-principles calculations and machine learning.

For a comprehensive understanding of the electronic, structural, optical and thermoelectric properties of K3ClCh (S, Se, Te) chalcohalide antiperovskites, first-principles calculations were employed utilizing WIEN2k, which uses the full-potential linearized augmented plane wave method. LDA, GGA, and mBJ, along with YS-PBE0 exchange correlations, were employed in this study to obtain the band gaps. The obtained findings demonstrate that the examined K3ClCh (S, Se, Te) compounds have a cubic structure and are characterized as direct band semiconductors with mBJ band gap values of 3.37 eV, 3.26 eV, and 3.31 eV, respectively. Encompassing the investigated optical properties of K3ClCh (S, Se, Te) chalcohalide antiperovskites, the dielectric response and optical absorption coefficient were determined, reaching an energy range of 13.6 eV. The studied compounds display an extended absorption band on the order of approximately 104 cm-1 in the ultraviolet spectral region, indicating their potential application in optoelectronics. The thermoelectric response with respect to temperature demonstrates optimized thermoelectric characteristics with contributions from phonon-mediated thermal conductivity. At 1000 K, the K3ClCh (S, Se, Te) chalcohalide antiperovskites exhibit ZT values of 0.70, 0.74 and 0.66, respectively. ML models were developed for predicting the PBE band gap of the investigated compounds. XGBoost outperformed other models, with low RMSE and high R2 values. The obtained results suggest that the investigated compounds are a good choice for optoelectronic and thermoelectric applications.