Comparative density functional theory and density functional tight binding study of 2-anthroic acid on TiO2

Highlights: • First comparative DFTB–DFT study of a dye–TiO₂ interface. • First ab initio study of 2-anthroic acid adsorption on titania. • DFTB vs DFT: qualitative and quantitative differences in adsorption properties. • Electronic structure qualitatively wrong with DFTB, right with DFT. A comparative DFTB (density functional tight binding)–DFT (density functional theory) study of several adsorption modes of 2-anthroic acid on titania is presented. Two parameterizations of DFTB previously used for dye–TiO₂ interfaces are tested. DFTB predicts adsorption energies which differ from those computed by DFT not only in magnitude (by up to 0.5 eV) but also in the order among different configurations. The band alignment computed with DFTB is not consistent with DFT results and with experimental data. The strategy of geometry optimization with DFTB followed by single-point DFT calculations also does not necessarily result in plausible adsorption energies.