Polaronic interactions between oxygen vacancies in rutile TiO2

Abstract

Oxygen vacancy-vacancy interactions in rutile $\mathrm{Ti}{\mathrm{O}}_{2}$ are studied in conjunction with polaron formation trends using density functional theory calculations. It is found that polarons strongly enhance the formation of oxygen vacancies in this material and also mediate the interactions between existing vacancies. At distances below 1 nm, two isolated and charge-neutral vacancies exhibit attractive interactions with an equilibrium distance of about 4 \AA{}. The attractive forces between vacancies partly arise from the polaronic transfer of excess electrons to reduce the potential energy. These discoveries provide microscopic explanations to the vacancy clustering phenomena, as well as a practical approach to stabilize the polarons at arbitrary Ti atoms in $\mathrm{Ti}{\mathrm{O}}_{2}$.