Light impurity effects on the electronic structure in TiAl

By using first-principles DMol and the discrete-variational method (DVM) based on density functional theory, we investigated the effect of some light impurities, H, B, C, N and O, on the electronic structure of their corresponding different impurity-doped systems in gamma-TiAl. The impurity formation energy, Mulliken occupation, bond order and charge density difference have been calculated to study the impurity-induced changes in the energetics and electronic structure. According to the impurity formation energy, it is found that the impurities energetically prefer to occupy the Ti-rich octahedron interstitial sites in the order H < B < O < N < C. Charge transfer suggests that the effect of the impurities is localized and the bond order as well as charge density difference results show that B, C and N are beneficial for the ductility of TiAl, while H and O are not.