A comparative theoretical investigation of optoelectronic and mechanical properties of KYS 2 and KLaS 2

• Published in: Materials science in semiconductor processing 2020, Vol.113
• Main Authors: Allal, Adel, Halit, Mohamed, Saib, Salima, Azzouz, Lahcene, Maabed, Said, Bouchenafa, Mohamed, Ahuja, Rajeev
• Format: Article
• Language: English
• Subjects: Elastic constants; Electronic structure; First-principles study; Ternary sulfides; Thermodynamic properties
• ISSN: 1873-4081; 1369-8001
• DOI: 10.1016/j.mssp.2020.105048

The ternary sulfides KYS 2 and KLaS 2 are two promising candidates for numerous applications, as much as white LED, X-ray phosphor and transparent conductor materials. However, theoretical studies on these materials are lacking, and many of their physical properties are still unknown. The aim of this work is to investigate the physical properties of the ternary sulfides KYS 2 and KLaS 2 namely, structural, elastic, optoelectronic, thermodynamic analysis, and set the substitution effect of Y and La elements in the two compounds. The fundamental properties calculations are based on ab-initio pseudopotential framework, with both local density approximation (LDA) and generalized gradient approximations (GGA) along with an expanded set of plane waves. The Becke, 3-parameter, Lee–Yang–Parr (B3LYP) hybrid functional is also employed to describe the electronic structures and optical properties. The optimized crystal parameters are correlated very well with the existing experimental data. The predicted values of the elastic constants demonstrate that the two compounds are mechanically stable and can be classified as brittle materials. The band structure analysis reveals that both KYS 2 and KLaS 2 have indirect band gap. The optical properties, like the refractive index, extinction, absorption and reflectivity coefficients, are determined for various polarizations of incident light, while both compounds present optical anisotropy. The obtained optical properties indicate the high transparency of KYS 2 and KLaS 2 in the infrared and visible regions, which makes them promising candidates for many of transparent applications. The thermodynamic properties are investigated with the help of quasiharmonic Debye model approximation. KYS 2 has a larger bulk modulus value, which make it more beneficial in engineering applications. Calculations of thermodynamical properties indicate that KYS 2 compound has better thermal conductivity, stronger chemical bonds and bigger hardness.