Investigation of Electrical, Structural and Optical Properties Zirconium disulfide (ZrS2) and Zirconium Selenium Sulfide (ZrSeS) using DFT and DFT + U

The electronic, structural, and optical properties of layered transition metal dichalcogenides, Zirconium disulfide (ZrS ₂ ) and Zirconium Selenium Sulfide (ZrSeS), with trigonal structures, were comprehensively investigated using density functional theory (DFT). Calculations employed various approximations including the LDA, GGA, PBE + U, and PBE0, within the Quantum-ESPRESSO framework. Rigorous convergence tests were conducted to ensure computational accuracy for both materials. The calculated equilibrium lattice constants for both ZrS ₂ and ZrSeS demonstrate good agreement with existing experimental data, validating the chosen computational methods. Analysis of electronic properties revealed that LDA and GGA significantly underestimate the band gap values for both compounds. In contrast, the PBE0 and the PBE + U approach yielded band gap values that are consistent with experimental results for ZrS ₂ and ZrSeS. The observed differences in band gaps are attributed to the distinct chemical and physical properties of sulfur and selenium. Furthermore, the optical properties, including the absorption spectrum, complex dielectric function, refractive index, and static and dynamic polarizability of both ZrS ₂ and ZrSeS in the trigonal phase were thoroughly studied. Key energy levels corresponding to significant electronic transitions and their intensities were identified. The study also explored anisotropic behavior the materials.