Effect of Nb doping on electronic structure of TiO₂/NiTi interface: A first-principle study

The electronic structure of pure and Nb doped TiO₂/NiTi interface have been calculated with the first-principle ultrasoft pseudopotential approach of the plane wave based on the density functional theory aiming at examining the effect of Nb on the electronic structure of the TiO₂/NiTi interface. The formation energy calculation results show that the structure with Ti-terminated NiTi matrix and O-terminated TiO₂ layer (Ti/O interface) is the most stable one among the four possible interface structures. Based on the optimized Ti/O interface model, the calculation results of the partial density of states, charge population and bond order suggest that the introduction of Nb on the interface strengthens the atomic interactions on the interface, as well as the interactions between the matrix and the oxidation layer in the neighborhood of the interface, which results in the improvement in the interfacial adhesion and the oxidation resistance of NiTi intermetallic compound.