Density functional approaches for the interaction of metal oxides with small molecules

The density functional tight-binding (DFTB) and time-dependent DFTB (TD-DFTB) methods are here extended. The incorporation of one-center exchange-like terms in the expansion of multicenter integrals leads to a DFTB scheme in which the fluctuation of the dual density matrix is treated self-consistently. This formalism improves upon hydrogen bond energies of neutral, protonated and hydroxide water clusters as well as of methylimidazole-water complexes. An analogous correction for TD-DFTB leads to marked qualitative and quantitative improvements over the original method. These formalisms are employed to investigate the structural and optical properties of titanium dioxide complexed with nitric oxide and acetaldehyde. Additionally, density functional theory (DFT) and DFTB are employed to investigate the structural and electronic properties of the interfaces between zinc oxide and several organic molecules.