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.

Automated summary

Density functional theory was employed to investigate the properties of Ti3C2 monolayer, both in pure and functionalized forms. The results showed that the pristine Ti3C2 and halogen-terminated structures were dynamically stable metals without energy band gaps. The surface-terminated Ti3C2 by halogen atoms was determined to be a novel functionalized monolayer material. The electronic band structure and density of states analysis confirmed the metallic nature of Ti3C2 in all terminated structures. Calculation of the Partial Density of States revealed that C atoms made a larger contribution to high-frequency optical modes, while Ti and halogen atoms dominated the low-frequency optical modes. The absence of an optical band gap was attributed to the metallic electronic structure of Ti3C2 and its functionalizations. These findings suggest the potential for tuning the optical properties of MXene by modifying the surface termination atoms.