Oxygen deficiency inTiO2: Similarities and differences between the Ti self-interstitial and the O vacancy in bulk rutile and anatase

\mathrm{Ti}{\mathrm{O}}_{2}is an oxygen-deficient, intrinsically ntype material, but it is often debated whether the electrons are donated by oxygen vacancies ({\mathrm{V}}_{\mathrm{O}})or titanium interstitials (\mathrm{T}{\mathrm{i}}_{\mathrm{i}}) Investigating this issue is complicated by the fact that rutile can self-trap electrons in intrinsic small polaron states, while bulk anatase cannot. The screened hybrid functional HSE06...