Quantum Insights into Hydrogen Storage and Optoelectronic Performance in Selenadiazoles: A DFT-Driven Approach to Future Innovations

Abstract

The structural, opto-electronic, hydrogen storage, and mechanical properties of H₈C₃N₂X(X = S, Se) were investigated using the density functional theory and the Wien2k code, which is based on the full potential linearized augmented plane wave method. The formation energy has confirmed the stability by − 2.58 eV and − 3.69 eV, respectively. The phonon dispersion analysis confirms the systems’ dynamical stability through the fundamental modes observed in the phonon spectrum. The band gap of the examined material was adjusted for application in renewable energy devices, ranging from 2.0 to 1.8 eV. The optical properties, such as dielectric function, absorption coefficient, refractive index, and reflectivity, were calculated from 0 to 14 eV. The particular electronic states that contribute to the band structure are highlighted by a density of states analysis for selenadiazoles; H-p, X-s/p, N-s/p, and C-s orbitals mainly shape the valence and conduction band, showing semiconducting nature of H₈C₃N₂X(X = S, Se). The charge density distribution was used to evaluate the nature of chemical bonds, revealing a mixed-bond semiconductor with low ionicity and high covalence. The mechanical properties of compounds are also examined to meet the Born stability criteria. The Cauchy pressure and Pugh criteria found these materials brittle and hard, as observed by elastic anisotropy. In the low-energy range, all-optical properties are shown to be appropriate for storing hydrogen. Furthermore, the gravimetric ratios of 4.2 wt% and 3.0 wt% indicated that all the compounds are acceptable for long-term hydrogen storage as a fuel and might significantly contribute to a wide range of power and transportation applications.