Study On The Doped Titanium Dioxide By First Principles

Titanium oxide films are widely researched for their excellent thromboresistance. Recently, it has become a hot field that how to improve the blood compatibility of titanium oxide films. Especially, the titanium oxide films doped with H, P, Ta, Nb have displayed an outstanding thromboresistance and showed a common characteristic of n-type semiconductor. In this paper,we built the model of TiO₂ doped with P, Al, Ta, H by the computer simulation technology and investigated the influence of doping different atoms with different styles on the band structure of TiO₂.In this thesis, we calculated the model of doped TiO₂ by First-principles method,which was based on the computational simulation methods and applied in materials research field. Some important concepts, such as Density Functional Theory (DFT), Local Density Approximation (LDA), Generalized Gradient Approximation (GGA), were explained and used. The function and application of CASTEP software pack, which was employed in this experiment, was also presented. The model used in this thesis was from the standard structure storeroom. The parameter setting and the veracity of the model was confirmed by calculating the essential structure and comparing the data with other researchers.Based on this, the super-cell model of doped TiO₂(anatase and rutile) was built. The structure was optimized under First-principles method joined with Generalized Gradient Approximation. In that way, we found the stabile structure with lowest energy of doped TiO₂ The result showed that the decisive factors of crystal lattice aberration was the symmetry of the doped place and the difference between doped atomic and replaced atomic.Base on the result of structure optimization, the electronic band structure, density of states of doped TiO₂ were calculated with First-principles method combing with Local Density Approximation. The calculation results showed that the doped TiO₂ had a noticeable effect on the band structure by choosing atoms and doping styles. When the doped bands located in the middle of the band gap or on the bottom of conduction band, the band gap would change obviously. P, Ta and H doped TiO₂ could form n-type semiconductor because their fermi level was moved to the bottom of conduction band. It can be suggested that the 3p state of P, t_2g state of Ta and 1s state of H played a significant role.