First-Principles Calculations of Polarons in Rutile and Anatase TiO₂

Titanium dioxide (TiO₂) has been an important technological material in many applications, such as photocatalysis and solar cells, but the polaronic nature of its charge carriers remains debatable despite few-decades theoretical and experimental investigation. Here, employing the newly developed method by our group, we report a systematic numerical study on the two most common polymorphs of TiO₂, rutile and anatase phase. The adopted method can bypass the requirement of using a large supercell and eliminate the self-interaction error when doing DFT simulations of polarons, two shortcomings that are often blamed for the compromised reliability of modeling of polarons. With the new methodology, we will compute the electron- and hole-polaron formation energies, electronic wave functions, lattice distortions, and their spectral decompositions into individual Bloch states and phonon modes, shedding light on the most important factors influencing the polaronic physics of TiO₂. Meanwhile, we will demonstrate how the addition of Hubbard U correction, a common practice when modeling polarons in TiO₂, will impact calculation results in the context of new methodology.