Structural growth sequences and electronic properties of zinc oxide clusters (ZnO)n (n=2-18)

The structural and electronic properties of (ZnO)(n) (n = 2-18) clusters are studied using gradient-corrected density-functional theory (DFT). The starting structures are generated from empirical genetic algorithm simulations or handmade constructions with chemical intuition. The lowest-energy structures of (ZnO)(n) are then selected from a number of structural isomers via DFT optimization. For small clusters (n = 2-7), ring structures were found to be the most stable. Three-dimensional cage and tube structures become energetically preferable for larger clusters (n = 9-18), and the competition between cage and tube structures leads to the alternative appearance of these two types of structures as global minima. The size evolution of electronic properties for zinc oxide clusters from ring toward cage or tube is discussed.