Tag Archives: Stefan Ernest Huber

Large-scale SCC-DFTB calculations of reconstructed polar ZnO surfaces

Authors: Stefan E. Huber, Matti Hellström, Michael Probst, Kersti Hermannson, and Peter Broqvist

We present a theoretical study of a range of surface znodefects for the most abundant polar ZnO(0001) surfaces using a tight binding approach with self-consistent charges (SCC-DFTB). We find that a combination of triangular pits at the Zn-terminated surface and a strongly ordered hexagonal defect pattern at the O-terminated surface constitutes a very stable reconstruction, in excellent agreement with experimental findings. On the whole, the SCC-DFTB method describes the polar surfaces of ZnO very well, and at a low computational cost which allows for the investigation of larger – and more realistic – surface structures compared to previous studies. Such large-scale calculations show that, at the Zn-terminated surface, the reconstruction results in a high density of one-layer deep triangular pit-like defects and surface vacancies which allow for a high configurational freedom and a vast variety of defect motifs. We also present extensive tests of the performance of the SCC-DFTB method in comparison with DFT results.

Surface Science 628, 51 (2014)

DOI: http://dx.doi.org/10.1016/j.susc.2014.05.001

An SCC-DFTB Repulsive Potential for Various ZnO Polymorphs and the ZnO-Water System

Authors: Matti Hellström, Kjell Jorner, Maria Bryngelsson, Stefan Ernest Huber, Jolla Per Kullgren, Thomas Frauenheim, and Peter Broqvist

We have developed an efficient scheme for the generation of accurate repulsive potentials for self-consistent charge density-functional based tight-binding calculations, which involves energy-volume scans of bulk polymorphs with different coordination numbers.

The scheme was used to generate an optimized parameter set for various ZnO polymorphs. The new potential was subsequently tested for ZnO bulk, surface, and nano-wire systems as well as for water adsorption on the low-index wurtzite (10-10) and (11-20) surfaces. By comparison to results obtained at the density functional level of theory, we show that the newly generated repulsive potential is highly transferable and capable of capturing most of the relevant chemistry of ZnO and the ZnO/water interface.

J. Phys. Chem. C, 117, 17004 (2013).
DOI: 10.1021/jp404095x