Strain-Tunable Electronic and Optical Properties of Monolayer CrS 2 : A First-Principles Investigation

The structural, electronic, and optical properties of monolayer CrS 2 under biaxial strain are systematically investigated using density functional theory. The material exhibits dynamic and mechanical stability with pronounced isotropy, sustaining ultimate tensile stress of 4.04 N/m at ~16% strain. Electronic analysis reveals CrS 2 as a direct-band-gap semiconductor with E g ≈ 0.96 eV. Tensile strain monotonically decreases the band gap, inducing a direct-to-indirect transition and eventual gap closure. Compressive strain drives nonmonotonic evolution: an initial increase at small strain followed by gradual decrease. Optical analysis demonstrates a high refractive index and strong broadband absorption spanning infrared to ultraviolet, both highly strain-sensitive. Strain-induced modifications are accompanied by significant shifts in critical points, particularly the valence band maximum. These findings establish mechanical strain as an effective tuning parameter for CrS 2 , with promising applications in flexible electronics, nanoelectromechanical systems, and strain-engineered optoelectronic devices.