Investigation of the optical and electronic properties of functionalized Ti3C2 Mxene with halid atoms using DFT calculation

Density functional theory is used to investigate the structural, electrical, and optical properties of the pure and functionalized Ti3C2 monolayer. The results illustrated that the pristine Ti3C2 Mxene and terminated ones with halogen atoms are dynamically stable metals with no energy band gap. The calculation of the phonon band dispersion depicts that the surface terminated Ti3C2 by halids is the dynamically stable novel functionalized monolayer material. The electronic band structure and density of states investigations demonstrate that all terminated monolayer structures preserve the metallic nature of Ti3C2. The calculated Partial Density of States (PDOS) shows a negligible contribution of the Ti atoms in the high-frequency optical modes compared with C atoms, while in the low-frequency optical the largest contribution belongs to the Ti and halogen group atoms. In the visible light energy range, a discrepancy between the in-plane and out-plane properties was calculated. Because of the metallic electronic structure of pristine Ti3C2 and its functionalizations, the optical band gap is not observed for all structures. Our calculated results represent the probability of tuning the optical properties of MXene by varying the surface termination atoms.