Structural, mechanical, electronic, and optical properties of SnBr2 and SnS2 as functional ceramic semiconductors for optoelectronic and energy applications

Abstract

This work presents a comprehensive first-principles investigation of the structural, mechanical, electronic, and optical properties of layered SnBr₂ and SnS₂ compounds, with particular emphasis on their potential as functional ceramic semiconductors. Calculations were performed within the framework of density functional theory using the full-potential linearized augmented plane wave method as implemented in the Wien2k code. Structural optimization was carried out using the generalized gradient approximation, while the modified Becke–Johnson potential was employed to achieve improved accuracy in describing electronic and optical properties. The results confirm that both compounds crystallize in a stable hexagonal structure belonging to the P6₃/m space group and exhibit direct band-gap semiconducting behavior, with band gap values of 2.88 eV for SnBr₂ and 2.39 eV for SnS2. Elastic properties indicate mechanical stability, with SnBr₂ showing a ductile tendency and SnS₂ showing a brittle tendency according to the Pugh criterion SnS₂ shows higher mechanical rigidity and stronger bonding characteristics compared to SnBr₂, highlighting its suitability for ceramic-based functional applications. Optical analysis reveals absorption coefficients on the order of 10⁵ cm⁻¹ in the ultraviolet region, along with high refractive indices, indicating appreciable optical response and electronic polarizability. These properties, combined with their calculated band-gap values, suggest that SnBr₂ and SnS₂ are potential candidates for ceramic-based optoelectronic devices, UV/visible photodetectors, optical absorbers, and optical-coating applications. Overall, this study provides fundamental insights into the structure–property relationships of Sn-based layered compounds and highlights their potential as functional ceramic semiconductors for optoelectronic and optical-coating applications. This is supported by the clear effect of anion chemistry on the calculated properties, where SnS₂ shows stronger bonding and higher mechanical rigidity than SnBr2, while both compounds maintain dynamical stability, direct band gaps, and appreciable optical absorption.