Oxygen vacancy related distortions in rutileTiO2nanoparticles: A combined experimental and theoretical study

The effects of doubly ionized oxygen vacancies $({{V}_{\mathrm{O}}}^{2+})$ on the electronic structure and charge distribution in rutile $\mathrm{Ti}{\mathrm{O}}_{2}$ are studied by combining first-principles calculations based on density functional theory and experimental results from x-ray photoelectron and x-ray absorption measurements carried out in synchrotron facilities on rutile $\mathrm{Ti}{\mathrm{O}}_{2}$ nanoparticles. The generalized gradient approximation of the Perdew-Burke-Ernzerhof functional has demonstrated its suitability for the analysis of the ${{V}_{\mathrm{O}}}^{2+}$ defects in rutile $\mathrm{Ti}{\mathrm{O}}_{2}$. It has been found that the presence of empty electronic states at the conduction band shifted $\ensuremath{\sim}1\phantom{\rule{0.28em}{0ex}}\mathrm{eV}$ from ${t}_{2g}$ and ${e}_{g}$ states can be associated with local distortions induced by ${{V}_{\mathrm{O}}}^{2+}$ defects, in good agreement with Gauss-Lorentzian band deconvolution of experimental O $K$-edge spectra. The asymmetry of ${t}_{2g}$ and ${e}_{g}$ bands at the O-$K$ edge has been associated with ${{V}_{\mathrm{O}}}^{2+}$, which can enrich the understanding of studies where the presence of these defects plays a key role, as in the case of doped $\mathrm{Ti}{\mathrm{O}}_{2}$.