First-principles study of electronic, optical, and thermoelectric properties of KMCuS 3 (M = Th and Sm) quaternary chalcogenides.

Copper-based quaternary chalcogenides are considered as intriguing material systems in terms of their remarkable optoelectronic and thermoelectric properties. Here we investigated the light interaction and electronic transport properties of novel KMCuS 3 (M = Th, Sm) materials. Advanced computations based on density functional theory were used for these calculations. The PBE-GGA scheme predicted band gaps for the KSmCuS 3 and KmThCuS 3 were 0.61, and 2.03 eV, respectively. While the TB-mBJ computed band gap values for KSmCuS 3 and KThCuS 3 were 0.91, and 2.39 eV, respectively. A direct band gap nature for both materials was confirmed by identifying the CBM and VBM at the same high symmetry gamma point. The Cu-d, Sm-f, Th-f, and S-p orbitals unified to form the valence band region at the BZ high symmetry point, while the Th-d and Sm-d orbitals formed the conduction band region. Furthermore, linear optical properties such as complex dielectric function components, along with other important optical parameters were computed and explained for possible employment in optoelectronic devices. The considerable thermoelectric characteristics were also predicted, and the incredible outcomes were described, implying that these compounds have potential for thermoelectric applications.