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

We present a theoretical study of a range of surface defects for the most abundant polar ZnO(0001)/(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. •Polar surface reconstructions are studied with SCC-DFTB for the first time.•SCC-DFTB results agree well with both experiment and DFT calculations.•Zn-terminated ZnO(0001) favors triangular pit-like defects and surface vacancies.•O-terminated ZnO(0001¯) favors a hexagonal defect pattern with zincblende stacking.•The most stable reconstructions have surface stoichiometries within a narrow range.