DFTB+ – An approximate DFT method: applications to computational nanomaterials

The new release of DFTB+ as a density-functional (DFT)-based approach, combining DFT-accuracy and Tight-Binding (TB) efficiency, is reported; http//:www.dftb.org. Methodological details and recent extensions to improve reliability and accuracy will be described briefly. Advanced functions include spin degrees of freedom, time dependent methods for excited state dynamics, and multi-scale QM/MM/Continuum-techniques to treat reactive processes in nanostructures under environmental conditions. Additionally, the combination with non-equilibrium Greens functions allows simulation of quantum transport in nanostructures and on the molecular scale.
As one latest application chemical vapor deposition (CVD) graphene growth on Cu-(111) has been modeled with DFTB molecular dynamics simulations. These simulations demonstrate at the atomic level how high-quality graphene forms on Cu-(111) surfaces. In contrast to other popular catalysts, such as nickel and iron, copper is in a surface molten state throughout the graphene growth at CVD-relevant temperatures supporting 5- and 7- membered ring defects to heal over time. In another application we report on excited-state theoretical simulations and experimental studies to investigate the degradation of nitric oxide and acetaldehyde on TiO2 under VIS and UV irradiation revealing charge transfer complexes on TiO2 as new source for visible light activity.