First-principles study of the vacancy and layer defects in Ti₃SiC₂

Abstract

First-principles calculations are performed to study the effects of defect on the structure and electronic properties of Ti3SiC2. The calculations show that the formation energy of Si vacancy is minimal compared with the Ti or C vacancies in Ti3SiC2. The defects of Si layer also can be formed under high-temperature or irradiation environments. The C-layers or Ti-layers are almost impossible to form. If the Si vacancy or Si layers are formed, they prefer to be substituted by the O and H atoms to form the MXene structure, and the unit cell of Ti3SiC2 lattice constant decreases in c-direction. However, it has quite slight effect on electronic properties of Ti3SiC2. The He impurities are almost impossible to occupy the Si vacancies, because the formation energy are 50.860 eV for one layer of Si atoms substituted by the He atoms. This type of defect leads to the lattice constant of Ti3SiC2 in c-direction increasing considerably. Therefore, Ti3SiC2 is a suitable candidate for nuclear materials because of the high-formation energies of He impurities under irradiation environment.