Using DFTB to Model Photocatalytic Anatase-Rutile TiO₂ Nanocrystalline Interfaces and Their Band Alignment

Band alignment effects of anatase and rutile nanocrystals in TiO₂ powders lead to electron-hole separation, increasing the photocatalytic efficiency of these powders. While size effects and types of possible alignments have been extensively studied, the effect of interface geometries of bonded nanocrystal structures on the alignment is poorly understood. To allow conclusive studies of a vast variety of bonded systems in different orientations, we have developed a new density functional tight-binding parameter set to properly describe quantum confinement in nanocrystals. By applying this set, we found a quantitative influence of the interface structure on the band alignment.