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991.
992.
993.
In general, both stoichiometric and catalytic reactions of organometallic complexes involve breaking and forming metal–ligand bonds. Therefore, an evaluation of the thermodynamics of such reactions requires the knowledge of metal–ligand bond energies (BDEs). The homolytic Fe? C bond dissociation energies [i.e., ΔHhomo(Fe? C)s] of 12 para‐substituted benzyldicarbonyl(η5‐cyclopentadienyl)iron, p‐G‐C6H4CH2Fp [1,G = NO2, CN, COMe, CO2Me, CF3, Br, Cl, F, H, Me, MeO, NMe2; Fp = (η5‐C5H5)(CO)2Fe] and 12 para‐substituted α‐cyanobenzyldicarbonyl (η5‐cyclopentadienyl)iron, p‐G‐PANFp [2,PAN = C6H4CH(CN)] were studied using Hartree–Fock (HF) and density functional theory (DFT) methods with large basis sets. The results show that BP86 and TPSSTPSS can provide the best price/performance ratio and more accurate predictions in the study of ΔHhomo(Fe? C)s. The B3LYP method satisfactorily predicts the α and remote substituent effects on ΔHhomo(Fe? C)s [ΔΔHhomo(Fe? C)s]. The fair correlations [r = 0.97 (g, 1), 0.99(g, 2)] of ΔΔHhomo(Fe? C)s of series 1 and 2 with the substituent σ constants imply that the para substituent effects on ΔHhomo(Fe? C)s originate mainly from polar effects, but those on radical stability originate from both spin delocalization and polar effects. The molecule stabilization effects (MEs) causes that not only the magnitude of ΔΔHhomo(Fe? C)s(1) varies significantly but also the direction changes from S‐pattern to O‐pattern. ΔΔHhomo(Fe? C)s(2) were found to conform to the Capto‐dative Principle. The detailed knowledge of the factors that determine the Fp? C bond strengths would greatly aid in understanding reactivity patterns in many processes. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
994.
The preparation process, crystallinity and electrical properties of pulse laser deposited Pb(ZrxTi1−x)O3 (PZT) thin films were investigated in this paper. PZT (x = 0.93) thin film samples deposited at different substrate temperatures were prepared. Si (1 1 0) was the substrate; Ag and YBCO were the top electrode and the bottom electrode respectively. The bottom electrode YBCO was deposited on the Si substrate by pulsed laser deposition (PLD), and then PZT was epitaxially deposited on YBCO also by PLD. After annealing, the top electrode Ag was prepared on PZT by thermal evaporation, and then the Ag/PZT/YBCO/Si structured thin films were obtained. The XRD and the analysis of their electrical characters showed that, when the substrate temperature was elevated from 600 °C to 800 °C, the crystallinity and electrical properties of PZT thin films became better and better, and the FR(LT)–FR(HT) phase transition of PZT (x = 0.93) thin films occurred at 62 °C. The PZT film deposited at 800 °C had the best pyroelectric properties, and when the FR(LT)–FR(HT) phase transition of this film occurred, the peak value of pyroelectric coefficient (p) was obtained, with a value of 1.96 × 10−6 C/(cm2 K). The PZT film deposited at 800 °C had the highest remnant polarization (Pr) and the lowest coercive field (Ec), with the values of 34.3 μC/cm2 and 41.7 kV/cm respectively. 相似文献
995.
Q. J. Zeng Z. Cheng J. -H. Yuan 《The European Physical Journal B - Condensed Matter and Complex Systems》2011,79(3):275-281
We present the calculations of the electronic structure
and transport properties on the filled-skutterudites
LaFe4Sb12 and CeFe4Sb12 using the
full-potential linearized augmented plane-wave method and the semi-classical
Boltzmann theory. Our calculation indicates that LaFe4Sb12 and
CeFe4Sb12 have the large density of states near the Fermi
level. The obtained Seebeck coefficient and the magnetic susceptibilities
are in good agreement with experimental results. It is found that n-type
doping in the CeFe4Sb12 compound may be more favorable than
p-type doping below 900 K and p-type doping in the CeFe4Sb12
compound may be more favorable than n-type doping above 900 K. It is also seen
that n-type doping in the LaFe4Sb12 compound may be more
favorable than p-type doping below 700 K and p-type doping in the
LaFe4Sb12 compound may be more favorable than n-type doping
above 700 K. Ultimately, we found that LaFe4Sb12 is more
suitable for thermoelectric applications than CeFe4Sb12. 相似文献
996.
H. Zeng J. Zhao J. W. Wei H. F. Hu 《The European Physical Journal B - Condensed Matter and Complex Systems》2011,79(3):335-340
The effects of nitrogen substitutional doping in the Stone-Wales (SW) defect on the electronic transport properties of zigzag-edged
graphene nanoribbon (ZGNR) are studied by using density functional theory combined with nonequilibrium Green’s function. The
transformation energies of all doped nanostructures are evaluated in terms of total energies and, furthermore, it is found
that the impurity placed on the center of the ribbon is the most energetically favorable site. Nitrogen substitution gives
rise to a complete electron backscattering region in doped configurations, and the location of which is dependent on the doping
sites. The electronic and transport properties of doped ZGNRs are discussed. Our results suggest that modification of the
electronic properties of ZGNR with topological defects by substitutional doping might not be significant for some doping sites. 相似文献
997.
Dong Zeng Shengteng Hu Alan N. Sayre Hamid Sarv 《Proceedings of the Combustion Institute》2011,33(2):1707-1714
The secondary reactions of volatile compounds, including coal tar and light gases, accounts for a great portion of soot formation and the subsequent heat release and pollutant emissions in the combustion zone. While coal primary pyrolysis has been extensively studied over the last few decades and several network pyrolysis models has been developed to describe this process, coal secondary pyrolysis is still not well understood. The Babcock and Wilcox Company has been investigating coal secondary pyrolysis in order to develop a comprehensive mechanism for inclusion in predictive computational fluid dynamics and coal combustion models. Supportive experiments were carried out in an entrained-flow reactor. Tar was extracted from the pyrolysis byproducts of seven coals of widely-distributed rank at temperatures ranging from 923 to 1473 K, and analyzed by 13C NMR. Tars formed from higher rank coals generally demonstrated higher sooting propensities. This rank-dependent sooting propensity is associated with tar’s chemical structure properties. With increased heat treatment severity, tar molecules lose a substantial amount of aliphatic attachments, and the average size of substitution per cluster decreases. Compared to tars formed from high-rank bituminous coals, those formed from low-rank sub-bituminous coals have a larger attachment portion, higher averaged substitution, and higher oxygen-containing functional groups. These differences contribute to the higher cracking propensity observed for low-rank coal tars. 相似文献
998.
Zeng LuTang Wanjun 《Physica B: Condensed Matter》2011,406(14):2901-2903
A series of NaY1−yEuy(WO4)2−x(MoO4)x (x=0−2 and y=0.06−0.15) phosphors have been prepared by a combustion route. X-ray powder diffraction, photoluminescence excitation and emission spectra were used to characterize the resulting samples. The excitation spectra of these phosphors show the strongest absorption at about 396 nm, which matches well with the commercially available n-UV-emitting GaN-based LED chip. Their emission spectra show an intense red emission at 616 nm due to the 5D0→7F2 electric dipole transition of Eu3+. As the Mo content increases, the intensity of the 5D0→7F2 emission of Eu3+ activated at wavelength of 396 nm increases and reaches a maximum when the relative ratio of Mo/W is 2:3. The intense red-emission of the tungstomolybdate phosphors at near-UV excitation suggests that the material is a potential candidate for white light emitting diode (WLEDs). 相似文献
999.
Wang X Zeng L Wiens M Schlossmacher U Jochum KP Schröder HC Müller WE 《Micron (Oxford, England : 1993)》2011,42(5):401-411
In the present study we examined material from the Ashikule Basin of Tibet. Chemical analyses were performed by use of energy dispersive X-ray spectroscopy and electron probe microanalysis to clarify whether the varnish layers that had developed on the surface of the rhyolite are indeed composed of varnish bodies and silica glaze. Electron microscopic analyses revealed that the surface of the varnish is covered both by filamentous hyphae bacterial and cocci-shaped forms. Within the varnish mineral layer in those samples two forms of bacteria-like microorganisms exist; cocci as tightly packed bacterial aggregates [within varnish bodies], and bacillus-like microorganisms [within the varnish matrix, that surrounds the varnish bodies]. The bacillus-like forms are embedded in a network of filaments that have diameters between 35 and 45 nm. These bacilli with the surrounding filaments are assumed to have been involved in biofilm formation (synthesis of extracellular polymeric substances) prior to their live burial. We concluded that the formation of the varnish layers was for the most part biogenically driven by microorganisms. 相似文献
1000.
合成了一种席夫碱结构的罗丹明B衍生物.研究表明,该衍生物能与Fe3+形成稳定配合物,同时伴随显著的荧光增敏和吸收增强.衍生物不仅对Fe3+呈现良好的荧光及比色探针性能,其与金属离子形成的配合物也是一种研究牛血清白蛋白的高灵敏荧光探钊. 相似文献