Pressure-Induced Modulation of Electronic and Optical Properties of Surface O-Functionalized Ti₂C MXene

Functionalized MXenes have gained increasing interest in the fields of thermoelectric materials, hydrogen storage, and so forth. In this work, pressure-induced band modulation and optical properties of the Ti₂CO₂ monolayer are investigated by using density functional theory with the hybrid (HSE06) functional. The calculation reveals that Ti₂CO₂ MXenes under pressure are stable because of the positive E _coh. Ti₂CO₂ undergoes a semiconductor-to-metal phase transition at about 7 GPa. The metallization of Ti₂CO₂ mainly results from the Ti-d state. Research indicates that there exist strong interactions between Ti-d and C-p, and Ti-d and O-p states, which are further confirmed by the charge analysis. In addition, the absorption is enhanced in the visible region with increasing pressure. We also observed some new absorption peaks in the visible region.