Structures of Zinc Oxide Nanoclusters: As Found by Revolutionary Algorithm Techniques

Abstract

We report the stable and low energy metastable structures of zinc oxide clusters, (ZnO) n , n ) 1-32, found using an evolutionary algorithm with polarizable shell interatomic potentials. This study comprises the first systematic search for nanoparticulate structures for this compound above n ) 18 and includes a comparison with other recent studies. As a function of n, global minimum and low energy metastable clusters evolve from rings (up to ca. 0.8 nm in diameter) to perfect closed bubbles (up to ca. 1.2 nm in diameter in the range reported), which are the structures that only contain tetragonal and hexagonal faces and all ions have a coordination number of three. The transition between the two structural families is blurred, with key structures that are also (i) open bubbles, which contain octagonal or larger faces, and (ii) bubbles that have handles, or two-dimensional ring fragments attached. A new nomenclature to describe these structures is defined. We find a greater stability of tetrahedral and trigonal coordinations compared to tetragonal for ZnO clusters in the range considered. Of the predicted global minimum clusters, spheroid cages n ) 12, 16, and 28, with symmetry point groups T h , T d and T, and barrels, which are a common motif, exhibit a relatively high stability. Bulklike wurtzite, or multilayered clusters, as well as the simple cuboid and related rock salt configurations are not found to be thermodynamically stable in the size range considered.

Atomistic and electronic structure of (X 2 O 3 ) n nanoclusters; n =1–5, X=B, Al, Ga, In and Tl

“…Two very different low-energy configurations for 1-1 compounds are found for compounds like ZnO: an octagonal ring and a cuboid (Al-Sunaidi et al 2008). Adding two oxygen atoms to these, we form configurations 2m and 2n, respectively.…”

“…The observation that a (X 2 O 3 ) 1 cluster can be constructed from a stable (XO) 2 cluster provides a possible method for generating (X 2 O 3 ) n clusters from (XO) 2n clusters, i.e. one can construct (X 2 O 3 ) n clusters from (ZnO) 2n global minima configurations found from a previous study (Al-Sunaidi et al 2008) and decorate the outer cations with the remaining n oxygen anions (with a maximum of one additional oxygen anion for each cation) to create potentially low-energy (X 2 O 3 ) n configurations. Below, such clusters will be noted.…”

“…First, we employ an EA technique (Al-Sunaidi et al 2008;Woodley et al 2010), implemented in the GULP package (Woodley et al 1999), to search for low-energy local minima (LM) on the RM energy landscapes of (Al 2 O 3 ) n and (In 2 O 3 ) n . Here, we assume that the set of lowest PBEsol0 energy LM structures can be readily obtained using standard local optimization techniques to refine the low-RM energy geometries obtained from the EA.…”

“…Note that rectangles represent inputs/outputs of different codes. (1) Our in-house version of the GULP (Woodley et al 1999;Al-Sunaidi et al 2008), (2) Materials Studio (Accelrys Software Inc.), (3) our in-house code PREGULP (Walsh et al 2011) and GULP (Gale & Rohl 2003), (4) a simple script and (5) FHI-AIMS Havu et al 2009). (Online version in colour.)…”

SnO-nanocluster modified anatase TiO2 photocatalyst: exploiting the Sn(ii) lone pair for a new photocatalyst material with visible light absorption and charge carrier separation

“…In terms of free (SnO) 3 cluster structure which is like zigzag it tends to create a more closed structure while adsorbed on anatase (001). The free (SnO) 4 nanocluster has a ring structure (similar to ZnO 95 nanoclusters of this size 48,49 ) and maintains this shape while adsorbed on anatase (001). 30 states at the top of the VB can also be determined from the PEDOS and we see the influence of the SnO lone pair, with these states originating from Sn 5s and O 2p states in the nanocluster.…”