Energy landscape of ZnO clusters and low-density polymorphs

Abstract

We report on an extensive study of ZnO materials with cage-like motives in clusters and bulk phases through structural searches using the minima hopping method. A novel putative ground state was discovered for the (ZnO)32 cluster with a tube-like structure, closely related to the previously reported (ZnO)24 ground state cage geometry. Furthermore, the effect of ionization on the geometries and energetic ordering of (ZnO)n clusters with n = 3 − 10, 12 was studied by directly sampling the energy landscape of the ionized system. Our results indicate that the transition from ring and planar structures to 3D cages occurs at larger cluster sizes than in the neutral system. Inspired by the bottom-up design philosophy and the predominance of cage-like structures in medium-sized clusters, a search for crystalline ZnO was conducted aimed specifically at low density polymorphs, resulting in the discovery of 57 novel metastable phases. The voids in these low-density materials closely resemble the hollow cage structures of small (ZnO)n/(ZnO) + n clusters with n < 16. In analogy to clathrate materials, these voids could serve to accommodate guest atoms to tailor the materials properties for various applications.

ZnO/ZnS (hetero)structures: ab initio investigations of polytypic behavior of mixed ZnO and ZnS compounds

“…At the start, we repeated the original local optimizations of the pure ZnO polytypes on ab initio level, using the CRYSTAL14 code, in order to establish quantitative compatibility with the calculations performed on ZnS and the mixed ZnO/ZnS compounds, for both LDA and HSE functionals. As in the earlier work, we found that the wurtzite polymorph of zinc oxide is the energetically lowest and thermodynamically most stable one, which is in agreement with experimental observations (Liu et al, 2013;Sowa & Ahsbahs, 2006;Kisi & Elcombe, 1989;Bates et al, 1962;Ves et al, 1990;Ö zgü r et al, 2005) and previous calculations (Catlow et al, 2008;Ostapenko et al, 2016;Boulfelfel & Leoni, 2008;Mora-Fonz et al, 2017;Sponza et al, 2015;Jaffe et al, 2000;Wang & Zhang, 2016;Demiroglu et al, 2014;Rasoulkhani et al, 2017;Lacerda & de Lazaro, 2017). As shown in Table S2 in the supporting information, when using LDA, all of the predicted ZnO polytypes (4H, 5H, 6H, 8H, 9R, 12R and 15R), as well as the sphalerite structure, exhibit essentially the same energy as the wurtzite modification.…”

“…lightemitting diodes, liquid crystal displays, etc. ), batteries and in optical materials, as well as additives to various materials, closely related to the structure-property relationships (Catlow et al, 2008;Demiroglu et al, 2014;Gerlach, 1922;Jaffe et al, 2000;Lao et al, 2002;Milek & Zahn, 2015;Ö zgü r et al, 2005;Peter et al, 2007;Rasoulkhani et al, 2017;Scott & Barnes, 1972;Sponza et al, 2015;Wang & Zhang, 2016;Wells, 1984).…”

Exploring the High-Pressure Materials Genome

“…Ideally, this fitness function corresponds to the Gibbs free energy, but it is often approximated by the potential energy (at zero pressure, temperature) or the enthalpy (at zero temperature) or some other biased energy landscape, and is sampled in an unconstrained manner in the configurational space. Many novel materials and their structures have been resolved using CSP at high pressures (8)(9)(10)(11), using chemical pressure and thermal degassing (12,13), as 2-dimensional materials (14)(15)(16), or at surfaces and interfaces (17)(18)(19)(20)(21). However, CSP approaches are computationally demanding and their applications are therefore often limited to small subsets of chemical spaces.…”

Structural, Electronic and Mechanical Properties of Few-layer Porous Nanosheet from Spheroidal Cage-like ZnO Polymorph

“…SOD, LTA, and FAU. On the basis of this approach we have found a novel nanoporous solid phases of (ZnO)16-cluster-assembled novel named as AST [14], which is later confirmed by extensive structural searches using the minima hopping method of ZnO cage-like bulk phases motifs [15]. Furthermore, the extended seek for the families of possible cage-like structures of individual clusters toward the nanostructured materials design has continue with several other high symmetric "magic cluster", e.g.…”