Computational studies on the structural, electronic, and optical properties of Ti2CO2 MXene using the (DFT + U) method

The structural, electronic, and optical properties of the Ti 2 CO 2 monolayer were systematically investigated using density functional theory (DFT) with (PBE-GGA + U) corrections. The optimal Hubbard parameters for Ti atoms were 4.72 eV using ultrasoft pseudopotentials (USPP) and 4.51 eV using norm-conserving (NC) pseudopotentials to accurately account for electron–electron interactions. The monolayer exhibits an indirect band gap, increased compared to standard (PBE-GGA) calculations. Partial density of states analysis shows that the valence band is dominated by C-2p and O-2p orbitals, while the conduction band is mainly composed of Ti-3d orbitals, governing optical transitions. The optical response displays strong anisotropy, with absorption onsets at 0.99 eV (E ∥ X) and 1.44 eV (E ∥ Z), and plasmonic maxima at 7.72 eV and 7.66 eV. Refractive indices at zero energy are 1.67 and 1.37, confirming anisotropic behavior. Electron–electron interactions shift peak positions and broaden spectral features. These properties make Ti 2 CO 2 a promising candidate for photodetectors, solar energy, photocalists, and transparent conductive coatings, providing a theoretical basis for experimental validation and guiding the design of multifunctional 2D MXene-based nanodevices.