First-principles investigations of structural, electronic and optical properties of cubic and tetragonal IrO2

Owing to its unique electronic structure and outstanding catalytic performance, IrO₂ holds great potential for applications in energy conversion and storage technologies. In this work, first-principles calculations were employed to comprehensively investigate the electronic structures, phase stability and optical properties of both cubic and tetragonal IrO₂, with the aim of uncovering their fundamental physical characteristics. The electronic structure analysis, including band structure, density of states, differential charge density, and Mulliken population, reveals that the O–Ir bonds in both cubic (C) and tetragonal (T) IrO₂ exhibit pronounced covalent characteristics, with stronger bonding observed in the tetragonal phase. Optical properties such as dielectric constant, reflectivity, and absorption coefficient were also analyzed. The dielectric constants ε₁ (0) of cubic and tetragonal IrO₂ were found to be 29.500 and 36.212, respectively. Additionally, IrO₂ exhibits significant absorption in the ultraviolet (UR) region, and its absorption coefficient gradually decreases with increasing laser wavelength. These findings underscore the strong potential of IrO₂, particularly its tetragonal phase-as a material for saturable absorbers in laser devices and as a cocatalyst for UR-driven photocatalysis applications, including water splitting and organic pollutant degradation.