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81.
Joo B. L. Martins Juan Andrs Elson Longo C. A. Taft 《International journal of quantum chemistry》1996,57(5):861-870
We investigated the adsorption and heterolytic dissociation of H2O and H2 molecules on a (ZnO)22 cluster corresponding to ZnO (0001), (000(OVERBAR)1), and (10(OVERBAR)10) surfaces using MNDO , AM 1 and PM 3 semiempirical procedures. The geometry of the adsorbed molecule has been optimized in order to analyze binding energies, charge transfer, and preferential sites of interaction. The adsorbed species interact most strongly when it is bonded to the twofold coordinated zinc atom of the cluster surface. The interaction of the H2O molecule with the surface of ZnO has a charge transfer from H2O to the surface ranging between 0.17 and 0.27 au. The neighboring atoms of the surface are the main receptors during the process of charge transfer. Our results indicate that there is a weak bonding of the hydrogen atom from OH with the oxygen surface atom that could produce the O(SINGLE BOND)H·O band. The interaction of the H2 molecule with the surface is generally weak and only the PM 3 method yields a strong binding energy for this interaction. There is a charge transfer from the H2 molecule to the surface. The chemisorption of H on oxygen atom of the surface transfer charge from the surface to the H. We also calculated the vibrational analyses for these interactions on ZnO surface and compared our results with available experimental data. © 1996 John Wiley & Sons, Inc. 相似文献
82.
Hinds S Taft BJ Levina L Sukhovatkin V Dooley CJ Roy MD MacNeil DD Sargent EH Kelley SO 《Journal of the American Chemical Society》2006,128(1):64-65
We engineer colloidal quantum dot nanocrystals through the choice of biomolecular ligands responsible for nanoparticle nucleation, growth, stabilization, and passivation. We systematically vary the presence of, and thereby elucidate the role of, phosphate groups and a multiplicity of functionalities on the mononucleotides used as ligands. The results provide the basis for synthesis of nanoparticles using precisely controlled synthetic oligonucleotide sequences. 相似文献
83.
DNA-surface conjugation is achieved through an intercalating molecular wire, resulting in more efficient electron transfer relative to systems utilizing conventional insulating tethers. 相似文献
84.
85.
86.
R. Haakenaasen E. Selvig S. Hadzialic T. Skauli V. Hansen J.E. Tibballs L. Trosdahl-Iversen H. Steen S. Foss J. Taftø M. Halsall J. Orr 《Journal of Electronic Materials》2008,37(9):1311-1317
HgTe nanowires have been grown by molecular beam epitaxy (MBE). They are nucleated at Au particles on Si or GaAs substrates
and subsequently self-organize and grow laterally on the surface into 20–50 nm wide, 0.5–1 μm long twisted, but single-crystal, wires. Further growth gives longer, wider, and straighter polycrystalline wires. When
unimpeded by Au particles on the surface, the wires become straight and consist of segments of cubic 〈111〉 HgTe and hexagonal
〈001〉 Te parallel to the wire. Te nanowires and Au␣nanowires have also occasionally been formed. All attempts to grow CdHgTe
on Si substrates with or without Au particles have resulted in polycrystalline layers. The phase diagrams and diffusion coefficients
imply that CdHgTe or HgTe nanowires will not grow by the vapor–liquid–solid technique at the low MBE growth temperatures.
SiO2 functions as a mask for selective growth of HgTe, but not for CdHgTe. 相似文献
87.
A. L. Almeida J. B. L. Martins E. Longo N. C. Furtado C. A. Taft J. R. Sambrano W. A. Lester 《International journal of quantum chemistry》2001,84(6):705-713
Ab initio calculations of large cluster models have been performed in order to study water adsorption at the five‐fold coordinated adsorption site on pure Mg(001) and MgO(001) surfaces doped with Fe, Ca, and Al. The geometric parameters of the adsorbed water molecule have been optimized preparatory to analysis of binding energies, charge transfer, preferential sites of interaction, and bonding distances. We have used Mulliken population analysis methods in order to analyze charge distributions and the direction of charge transfer. We have also investigated energy gaps, HOMO energies, and SCF orbital energies as well as the acid‐base properties of our cluster model. Numerical results are compared, where possible, with experiment and interpreted in the framework of various analytical models. © 2001 John Wiley & Sons, Inc. Int J Quant Chem, 2001 相似文献
88.
The electronic absorption spectra at 77 K of KFeS2, RbFeS2 and CsFeS2 were measured and the experimental bands were assigned on the basis of ligand-field theory regarding d5 high spin Fe3+ under a field of Td symmetry yielding Δ ≈ ?4500 to ?5000 cm?1. 相似文献
89.
The coupling between localized magnetic moments via conduction electrons is calculated taking into account the temperature and the mean free path of the electrons. For a fully degenerate electron gas and an infinite electronic mean free path the oscillatory RKKY interaction is obtained. On the limit of Boltzmann population and for infinite electronic mean free path the interaction can only be ferromagnetic. Taking into account the electronic mean free path the possibility of antiferromagnetism is restored. Furthermore the range of the interaction decreases. Several intermediate cases and possible applications are discussed. 相似文献
90.
Manganese oxide films have been grown by atomic layer deposition and investigated using electron diffraction and high-resolution electron microscopy (HREM). The films were deposited on the (001) surface of monocrystalline α-Al2O3. The films were found to consist of an ordered version of the hexagonal ε-MnO2 (Akhtenskite) type. Using X-ray diffraction, the cell parameters were determined to be a?=?2.75(2)?Å and c?=?4.302(5)?Å. The films are epitaxial with a specific orientation relative to the Al2O3 substrate. The [210] and [001] axes of ε-MnO2 are parallel to the [110] and [001] axes of α-Al2O3, respectively. Evidence of cation ordering was found by parallel beam electron diffraction. The ordered domains are needle shaped with widths of 2–10?nm. The unit cell of the ordered structure was found to be orthorhombic with cell dimensions a?=?2.75, b?=?4.76, c?=?4.302?Å and space group Pmnn (No. 58). 相似文献