Effects of aluminum vacancies on electronic structure and optical properties of Ta4AlC3: A first principles study

We investigated the effect of aluminum vacancies (VAl) on the structural, electronic and optical properties of Ta4Al1−xC3 (x=0, 0.25, 0.5, 0.75) based on the first-principle calculation using density functional theory. We found that the lattice constant a remains almost unchanged with the variation of VAl concentration, while c and c/a ratio decrease with increasing VAl concentration. Moreover VAl induced local distortions have significant influence on the electronic and optical properties of Ta4AlC3, especially beyond the critical VAl concentration (x=0.5). On the other hand, the presence of VAl can improve the dielectric properties of Ta4AlC3. From the optical properties analysis, we predicted that Ta4Al1−xC3 is not suitable as a coating material to avoid solar heating.