Rings, towers, cages of ZnO

Reber, Arthur C.; Hunjan, Jagtar Singh; Beltrán, Marcela R.

doi:10.1140/epjd/e2007-00087-7

Cited by 66 publications

(86 citation statements)

References 26 publications

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“…In experiments cluster populations are often ionized to facilitate control and avoid aggregation, which may lead to isomer selection via ease of ionization rather than only neutral energetic stability. We stress that this would be an experimentally dependent post-selection process on an [15,25]. Our DFT-refined global optimization calculations concur with this result but further find that the second highest energy isomer is a hitherto unreported distorted cagelike cluster lying 0:11 eV=ZnO above the ground state (see Fig.…”

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confidence: 80%

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Ultralow-Density Nanocage-Based Metal-Oxide Polymorphs

2007

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For two important metal oxides (MO, M=Mg, Zn) we predict, via accurate electronic structure calculations, that new low-density nanoporous crystalline phases may be accessible via the coalescence of nanocluster building blocks. Specifically, we consider the assembly of cagelike MO 12 clusters exhibiting particularly high gas phase stability, leading to new polymorphs with energetic stabilities rivaling (and sometimes higher) than those of known MO polymorphs. DOI: 10.1103/PhysRevLett.99.235502 PACS numbers: 61.43.Gt, 61.46.Bc, 71.15.Nc, 82.75.Fq Exhibiting a cubic crystal structure in its bulk equilibrium phase at ambient conditions, rock salt magnesium oxide (rs-MgO) is a prototypical example of a stable, densely packed insulating ionic system. Bulk ZnO may be stabilized in a cubic rock salt phase (rs-ZnO) under high pressure [1] but prefers to adopt a wurtzite ground state structure (wz-ZnO) under ambient conditions. ZnO is also a wide band gap semiconductor with (nano)technological potential in numerous applications (e.g., optoelectronics, sensors). Theoretical studies have examined numerous bulk polymorphs of MgO and ZnO [2,3] focusing mainly on known dense crystal phases exhibited in other materials. Under conditions of high temperatures [4] and/or reduced dimensionality (e.g., thin films [5]) studies have further reported strong evidence for alternative phases of MgO. At the nanoscale, recent interest in the properties of ZnO has been intense with theoretical predictions of hexagonal phases for various reconstructed [6,7] and strained nanostructures [8]. In all cases, the reported bulk or nanoscale phases are denser than the wz-ZnO phase for ZnO, and for MgO have maximum volumes per unit cell of up to 30% greater than rs-MgO. Our approach, considering clusters as building blocks [9], bypasses the constraint of considering known dense phases as sources of new polymorphs (e.g., via pressure-induced transformations), showing that it should be possible to stabilize new nanoporous polymorphic phases of both ZnO, with unit cell volumes between 20 -70% greater than wz-ZnO, and MgO, with unit cell volumes 50 -110% greater than rs-MgO. To our knowledge the polymorphs we propose have not been reported for any other MO material but have strong topological links with certain SiO 2 -based nanoporous crystals. Following the formation of silicate-based zeolitic phases we have attempted to assess the viability of our proposed polymorphs via nanoscale bottom-up routes using MO 12 cage clusters as building blocks via calculating (i) the thermodynamic and kinetic stability of MO 12 cages with respect to competing isomers and (ii) the energetics of cage-cage interactions. Via determining the equation of state (EOS) for each of our MO polymorphs, we find three phases with energies 0:15-0:27 eV=MO above their respective ambient ground states. Considering that the synthesized rs-ZnO polymorph lies 0:29 eV=ZnO above wz-ZnO these polymorphs seem attractive synthesis targets. Further, all our polymorphs have the lowest reported ...

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confidence: 80%

“…Comparing the relative energetic stability of ZnO 12 with cluster isomers possessing greater or fewer ZnO units also provides predictive measures of likely isomer abundances in a cluster population. Such stability measures are found to be peaked at n 12 [15,25] …”

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confidence: 96%

Ultralow-Density Nanocage-Based Metal-Oxide Polymorphs

2007

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“…In this way, a new type of ZnO structure (Zn 12 O 12 nanocage) has been extensively studied at theoretical level, where its spherical form is the most stable compared to other conformations [18][19][20][21]. On the other hand, the capacity of the Zn 12 O 12 to absorption different chemical species has been investigated: NO [22]; H atoms [23]; CO 2 [24]; H 2 S [25]; Cl 2 [6]; thiophene [26]; formic acid [27].…”

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confidence: 99%

Computational studies of the Ca12O12, Ti12O12, Fe12O12 and Zn12O12 nanocage clusters

Oliveira

Pires

Neto

et al. 2015

Chemical Physics Letters

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“…The ground states [3] and their excitation states [4] of small-sized (ZnO) n clusters with n = 1-15 were studied using density functional theory (DFT) and time-dependent DFT (TDDFT) methods, respectively. The low-spin structures and electronic properties of various sizes of (ZnO) n clusters (n = 9-64) [5], (n = 2-18, 21) [6], (n = 1-32) [7], (n = 2-18) [8], (n = 24, 28, 36 and 48) [9], (n = 1-32) [10], and Zn 3 O m (m = 3-5) [11] were theoretically characterized using various computational methods, and the optical properties of (ZnO) n clusters (n = 2-12) were studied using DFT method [12]. The zinc oxide clusters were studied by mass spectroscopic method, and the clusters of (ZnO) 34 , (ZnO) 60 , and (ZnO) 78 were found as the magic number clusters [13].…”

Section: Introductionmentioning

confidence: 99%

DFT investigation on molecular structures of metal and nonmetal-doped ZnO sodalite-like cage and their electronic properties

2015

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The optimized structures of the ZnO sodalite-like cages (ZnOSLs) doped by single metal atoms (Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Pd, Ag, Pt and Au) and single nonmetal atoms (B, C, N, Al, Si, P, Ga and Ge) were obtained using DFT/B3LYP method. The energetics and thermodynamic properties for doping processes of single metal atom to Zn V of the Zn vacancy defect ZnOSL surface, (ZnOSL ? Zn V ) and nonmetal atom to O V of the O vacancy defect ZnOSL surface, (ZnOSL ? O V ) were obtained. The binding abilities of transition metal dopants to Zn V of [ZnOSL ? Zn V ] and nonmetal dopants to O V of [ZnOSL ? O V ] surfaces are in orders: Crrespectively. Energy gaps and NBO partial charges for low-spin and high-spin states of metal and nonmetal-doped ZnOSLs and their analyses are reported. Graphical Abstract Keywords Low-spin Á High-spin state Á ZnO sodalite-like cage Á Metal doping Á Nonmetal doping Á DFT Á NBO Electronic supplementary material The online version of this article (

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Rings, towers, cages of ZnO

Cited by 66 publications

References 26 publications

Ultralow-Density Nanocage-Based Metal-Oxide Polymorphs

Ultralow-Density Nanocage-Based Metal-Oxide Polymorphs

Computational studies of the Ca12O12, Ti12O12, Fe12O12 and Zn12O12 nanocage clusters

DFT investigation on molecular structures of metal and nonmetal-doped ZnO sodalite-like cage and their electronic properties

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