Issue 28, 2017

Size dependent structural and polymorphic transitions in ZnO: from nanocluster to bulk


We report on an extensive survey of (ZnO)N nanostructures ranging from bottom-up generated nanoclusters to top-down nanoparticles cuts from bulk polymorphs. The obtained results enable us to follow the energetic preferences of structure and polymorphism in (ZnO)N systems with N varying between 10–1026. This size range encompasses small nanoclusters with 10s of atoms and nanoparticles with 100s of atoms, which we also compare with appropriate bulk limits. In all cases the nanostructures and bulk systems are optimized using accurate all-electron, relativistic density functional theory based calculations with numeric atom centered orbital basis sets. Specifically, sets of five families of (ZnO)N species are considered: single-layered and multi-layered nanocages, and bulk cut nanoparticles from the sodalite (SOD), body centered tetragonal (BCT), and wurtzite (WZ) ZnO polymorphs. Using suitable fits to interpolate and extrapolate these data allows us to assess the size-dependent energetic stabilities of each family. With increasing size our results indicate a progressive change in energetic stability from single-layered to multi-layered cage-like nanoclusters. For nanoparticles of around 2.6 nm diameter we identify a transitional region where multi-layered cages, SOD, and BCT nanostructures are very similar in energetic stability. This transition size also marks the size regime at which bottom-up nanoclusters give way to top-down bulk-cut nanoparticles. Eventually, a final crossover is found where the most stable WZ-ZnO polymorph begins to energetically dominate at N ∼ 2200. This size corresponds to an approximate nanoparticle diameter of 4.7 nm, in line with experiments reporting the observation of wurtzite crystallinity in isolated ligand-free ZnO nanoparticles of 4–5 nm size or larger.

Graphical abstract: Size dependent structural and polymorphic transitions in ZnO: from nanocluster to bulk

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Article information

Article type
20 Apr 2017
25 Jun 2017
First published
26 Jun 2017
This article is Open Access
Creative Commons BY license

Nanoscale, 2017,9, 10067-10074

Size dependent structural and polymorphic transitions in ZnO: from nanocluster to bulk

F. Viñes, O. Lamiel-Garcia, F. Illas and S. T. Bromley, Nanoscale, 2017, 9, 10067 DOI: 10.1039/C7NR02818K

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