First-principles study on ZnO nanoclusters with hexagonal prism structures

Size-dependent ground state energies and electronic structures of ZnO nanoclusters with wurtzite structures are investigated using density-functional theory calculations. After structural optimizations, the initial Zn-O double layers merge into single layers. Particularly, a phase transition from the four-coordinate wurtzite to the six-coordinate rocksalt structure is found in the ZnO cluster with 48 atoms, which indicates that clusters with too many dangling bonds will significantly change their configurations during the relaxations. The calculations also show that on the whole both the energy gap and the binding energy approach to the corresponding bulk values with increasing cluster size.