First-principle Study Of Anatase TiO₂（101） Surface

Based on the density functional theory （DFT） first principles method, thegeometry、electronic structure and optical properties of oxygen vacancy and C-dopedanatase TiO₂（101） surface were studied. And the oxygen vacancy diffusion andadsorption of O₂molecules on the surface were simulated. The following work havebeen done in this thesis:1. The oxygen vacancies point defect formation energy for anatase TiO₂（101）surface at different atmosphere were calculated and the calculation showed thatrelative to the oxygen-rich growth condition, Ti-rich growth condition was moreconducive to the surface energy stability and bridging oxygen vacancy was most likelyto be formed. The electronic structure analysis showed that the oxygen vacancie-dopedTiO₂was a degenerate semiconductor, the Fermi level enter into the conduction band,Mott phase transformation was occurred. The calculated results of optical propertiesshowed that the oxygen vacancy expanded the visible-light response range of TiO₂.2. Using the first principles molecular dynamics method, the diffusion of oxygenvacancy defects of anatase TiO₂（101） surface at different temperatures were studied.The changes of the total energy and geometry structure of surface O vacancy systemwere calculated. When the system reached thermodynamic equilibrium, the O vacancyactivation energy of diffusion was0.5555eV and the diffusion coefficient was2.66×10^-17m2s^-1.3. Based on the DFT first principles method，the most stable geometry structure ofC atom interstitial doping, the relationship between the C substitution formationenergy and the surface oxygen vacancies formation energy were disscussed. Thegeometry structure、band structure、density of states for C substitutional and interstitial doped anatase TiO₂（101） surface supercells were calculated and analysed in detail.4. The adsorption of O₂molecule on the anatase TiO₂（101） complete surface wassimulated. The results showed that the adsorption was physical adsorption and hadlittle impact on the geometry, electronic structure of the surface. The electronstransfered from the O₂molecule to the surface after adsorption.