First-Principles Investigation of the OsI\(_{2}\) Monolayer: A Novel Two-Dimensional Dihalide Material for Optoelectronic Applications

The study of two-dimensional (2D) materials has attracted considerable attention from material scientists globally, mainly because of their distinct electronic, spintronic, magnetic, and optoelectronic characteristics. Transition metal dichalcogenides (TMD) and dihalides (TMDH) are two examples of 2D materials. This study investigates the structural stability, phonon dispersion, electronic, optical, and thermodynamic properties of the unique trigonal osmium diiodide (OsI \(_2\) $_2^{}$ ) monolayer, which is an example of TMDH. The well-established Density Functional Theory (DFT) is employed for this purpose. We identified an indirect bandgap semiconductor property in this monolayer. The energy bandgap values for GGA-PBE, GGA-PBEsol, and the hybrid functional HSE06 were found to be 1.72, 1.56, and 2.86 eV, respectively. The compound OsI \(_2\) $_2^{}$ demonstrates structural stability, and studies of phonon dispersion indicate that there are no virtual (negative) phonon frequencies. Furthermore, OsI \(_2\) $_2^{}$ demonstrates optical absorption within the visible spectrum, making it suitable for optoelectronic applications. However, thermodynamic property calculations have shown that the synthesis of the OsI \(_2\) $_2^{}$ monolayer would occur naturally at temperatures lower than room temperature, as evidenced by the free energy estimates.