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We have studied the structures and stabilities of Al(13)I(n) (-)(n = 1-12) clusters at the density-functional level of theory. Unlike the case of Al(13)I(-), the Al(13)I(n) (-)(n=2-12) clusters do not have an Al(13) (-) core electronically. Population analysis shows that a significant charge transfer occurs from the Al cluster to the I atoms, where the populations for Al(13) vary from -0.48(Al(13)I(2) (-)) to +0.97(Al(13)I(12) (-)). Moreover, the shape of Al(13) moieties in the Al(13)I(n) (-) (n > or = 6 or 7) clusters is significantly distorted from the structure of Al(13) (-), an icosahedron, and is a "cagelike" form, which can be explained by both electronic and steric reasons. Our theoretical results are in good agreement with the experimental observations of Bergeron et al. [Science 307, 231 (2005)]. 相似文献
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Foroutan-Nejad C 《Physical chemistry chemical physics : PCCP》2012,14(27):9738-9748
The influence of presence of counter ions and π-complexation with benzene on the bonding and magnetic properties of Al(4)(2-), the most studied all-metal cluster, is studied here. It is shown that complexation by either counter ions or benzene decreases the delocalization index between Al atoms and the magnitude of bond magnetizability, that is a Quantum Theory of Atoms in Molecules, QTAIM, -based magnetic index of aromaticity. Benzene forms two types of π-complexes with the Al(4) framework; CH-π (T-shaped) complexes and parallel π-π stacking (PPS) complexes. It is shown that variation in the π-charge of the Al(4) framework affects the relative stability of the T-shaped/PPS complexes. Free Al(4)(2-) forms a stable T-shaped anion-π complex with benzene but in the presence of cations, formation of PPS complexes is more favourable, energetically. It is suggested that this property could be used for designing molecular switches and tuneable anion sensors. 相似文献
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《Journal of the Less Common Metals》1989,146(1-2):213-219
The phase behavior of the AlIr system has been studied using differential thermal analysis, electron microprobe analysis, X-ray diffraction, chemical analysis and X-ray fluorescence. Our work confirms the existence of four compounds: Al9Ir2, Al3Ir, Al2.7Ir and AlIr. We also observed an additional intermetallic phase, with a stoichiometry corresponding to Al13Ir4; however, this compound exhibits a complex X-ray pattern and currently no structure has been determined.Peritectic temperatures were determined for Al9Ir2 (900 °C), Al13Ir4 (1015 °C) and Al3Ir (1450 °C). The Al2.7Ir phase is stable to above 1450 °C, and the congruent melting temperature of AlIr is 2120 ± 20 °C. The solubility of aluminum in iridium was measured between 1085 and 1850 °C, and the maximum solid solubility was extrapolated to 18 at.% at 2058 °C. The maximum solid solubility of iridium in aluminum was measured to be less than 0.1 at.%. A phase diagram for the AlIr system is presented. 相似文献
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Uwe Klingebiel Mathias Noltemeyer Annette Wand 《Journal of organometallic chemistry》2006,691(12):2657-2665
Lithium salts of 2.6-dialkylanilines react with di-tert-butylfluorosilanes to give mono (1-3) - and bis (7, 8)-(2.6-dialkylphenylamino)silanes. Amino-2.6-dimethylphenyl-(di-tert-butylfluoro)silane (1) forms with BuLi a dimeric lithium salt (4) containing an eight-membered (LiFNSi)2 ring system. Thermally, 4 loses LiF and a bicyclic compound (9) via iminosilenes is obtained. The lithium salt of the bulkier amino-2.6-diisopropylphenyl-(di-tert-butylfluorosilanes) (5-7) thermally loses LiH and iminosilanes (10-12) with a 14π-system are isolated. The reaction mechanisms and crystal structures are discussed. 相似文献
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A. Janghorban A. Antoni-Zdziobek M. Lomello-Tafin C. Antion Th. Mazingue A. Pisch 《Journal of Thermal Analysis and Calorimetry》2013,114(3):1015-1020
The Al-rich phase equilibria in the Al–Zr binary system were investigated experimentally. The phase diagram for compositions up to 40 at.% Zr was determined experimentally by differential thermal analysis and metallography. Three stable intermetallic compounds exist in this region of the diagram: Al3Zr2, Al2Zr, and Al3Zr. The peritectic melting of Al3Zr2 and the congruent melting of Al2Zr were confirmed. Al3Zr, the most Al-rich intermetallic compound, melts peritectically, which contradicts information available in the literature. In addition, the reaction between Al3Zr and the (Al) solid solution seems to be of eutectic nature, in contradiction with previous results found in the literature. Based on these new experimental evidence, a revised phase diagram is drawn. 相似文献
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A. T. Adorno M. R. Guerreiro A. V. Benedetti 《Journal of Thermal Analysis and Calorimetry》2001,65(1):221-229
The thermal behavior of Cu—Al alloys with 17, 19 and 21 at.%Al was examined by differential thermal analysis (DTA), differential scanning calorimetry (DSC), X-ray diffractometry (XRD), optical microscopy (OM) and scanning electron microscopy (SEM). The presence of the gamma phase (Al4Cu9)was clearly detected for the Cu—19 at.%Al alloy and caused the 2 phase disordering process in two stages. The tendency to increase the 2 dissolution precipitates with the increase in the Al content seems to be reverted for compositions at about 21 at.%Al and the heating/cooling ratio seems to influence the thermal response of this process. The presence of the endothermic peak corresponding to the 1 transformation depends on an incomplete decomposition reaction. The variation of the heating rate showed that the 1(+1) decomposition is the dominant reaction for alloys containing 19 and 21 at.%Al.This revised version was published online in November 2005 with corrections to the Cover Date. 相似文献
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Mohammed A. Amin 《Arabian Journal of Chemistry》2013,6(1):87-92
The pitting corrosion susceptibility of pure Al and three Al-Si alloys, namely (Al-6%Si), (Al-12%Si) and (Al-18%Si) has been studied in 0.04 M KSCN solution. Measurements were carried out under the effect of various experimental conditions using cyclic polarization, potentiostatic and galvanostatic techniques. In all cases, the potentiodynamic anodic polarization curves do not exhibit active dissolution region due to spontaneous passivation. The passivity is due to the presence of a thin film of Al2O3 on the anode surface. The passive region is followed by pitting corrosion, at a certain critical potential, pitting potential (Epit), as a result of breakdown of the passive film by SCN? anions. Cyclic polarization measurements allowed the determination of the pitting corrosion parameters, namely the pitting potential and the repassivation potential (Erp). Alloyed Si decreased the passive current (jpass) and shifted both Epit and Erp towards more positive values. Thus alloyed Si suppressed pitting attack. The effect of illumination on passivity and the initiation of pitting corrosion on Al in KSCN solutions was also studied. It is observed that illumination of Al leads to an increase in its pitting corrosion resistance-apparent from jpass, Epit, and Erp measurements in aggressive KSCN solutions. 相似文献
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采用密度泛函理论的四种方法:杂化密度泛函B3LYP与B3PW91、Perdew-Wang91交换与相关泛函WP91PW91、局域自旋密度近似SVWN,研究了A15、Al5-和Al5+团簇的多种可能结构,找到了它们稳定的结构与自旋态,与已有的理论结果作了比较,并计算了Al5-的绝热与垂直电子离解能、Al5的绝热与垂直电离势,同有关的实验数据比较,符合较好.同时对四种密度泛函方法的计算结果作了一些比较与讨论. 相似文献
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Anna Maria Cardinale Daniele Macciò Stefano Delfino Adriana Saccone 《Journal of Thermal Analysis and Calorimetry》2011,103(1):103-109
The isothermal section of the Nd–Al–Si ternary system at 500 °C has been investigated using differential thermal analysis,
X-ray diffraction analysis, scanning electron microscopy and electron micro-probe analysis. Four ternary intermetallic compounds
were confirmed: NdAl2Si2 (τ1), hP5-CaLa2O2 structure type, Nd2Al3Si (τ2), hP3-AlB2 structure type, NdAl1−x
Si1+x
, 0.25 ≤ x ≤ 0.3 (τ3), tI12-αThSi2 structure type and Nd2Al1−x
Si1+x
, 0 ≤ x ≤ 0.2, (τ5), oS8-CrB structure type. A new ternary intermetallic phase (τ4) was found: Nd4Al3Si3, orthorhombic oS20, isotypic with Pr4Al3Ge3. 相似文献
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《印度化学会志》2023,100(2):100884
Catalytic hydrogenation of acetylene was studied with an ideal feed with a catalyst prepared from different alumina support and with varying quantities of promoter addition. Silver promoted palladium alumina catalysts were prepared on the transition alumina, ρ-alumina and the catalyst performance was compared with the traditional palladium alumina catalyst based on α-alumina. The catalyst supports were prepared using the granulation technique and sequential impregnation method was used for the catalyst preparation. The silver metal loading was varied in the catalysts and the impact of varied promoter quantity was also studied. The supports were characterized for the acidity, alumina phase, and catalyst characterization was done using TEM, TPR, and BET method to understand the difference between catalysts prepared on different types of alumina support. A fixed bed catalyst reaction was used for the performance evaluation and an ideal gas with acetylene and nitrogen was used as the feed. The catalyst evaluation gives the comparative performance of the catalysts at different temperature conditions. Acetylene conversion and ethylene selectivity in the product were evaluated. The spent catalyst analysis was done using TGA and CHN analysis was performed to understand the carbon deposition and by-product formation during the reaction with different types of catalysts. 相似文献
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Yu-Mi Kim Da-Som Kang Sung-Kil Hong Young-Chan Kim Chang-Seog Kang Se-Weon Choi 《Journal of Thermal Analysis and Calorimetry》2017,127(1):107-113
Ti-based amorphous alloys produced by ultra-rapid melt cooling represent an excellent option as biomaterials because of their mechanical properties and corrosion resistance. However, complete elimination of toxic elements is affecting the glass-forming ability and amorphous structure could be obtained only for thin ribbons or powders that are subsequently processed by powder metallurgy. Amorphous ribbons of special Ti42Zr40Ta3Si15 alloy, which is completely free of any toxic element, were produced by melt spinning, and the thermostability of resulting material was investigated in order to estimate its ability for further heat processing. Isochronal differential scanning calorimetry (DSC) was used to determine transformation points such as glass transition temperature T g or crystallization temperature T x. The activation energy for crystallization of amorphous phase was calculated based on Kissinger method, using heating rates ranging between 5 and 20 °C min?1. Amorphous structure of resulting ribbon was evidenced by means of X-rays diffraction (XRD) and high-resolution transmission electron microscopy (HR-TEM). It was determined that amorphous Ti42Zr40Ta3Si15 alloy has a high activation energy for crystallization, similar to other Ti-based amorphous alloys, which provides good thermal stability for subsequent processing, especially by means of powder metallurgy techniques. 相似文献
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Dr. Alba Gigante Eline Sijbesma Dr. Pedro A. Sánchez-Murcia Prof. Xiaoyu Hu Dr. David Bier Sandra Bäcker Prof. Shirley Knauer Prof. Federico Gago Prof. Christian Ottmann Prof. Carsten Schmuck 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(13):5322-5325
We report on a stabilizer of the interaction between 14-3-3ζ and the Estrogen Receptor alpha (ERα). ERα is a driver in the majority of breast cancers and 14-3-3 proteins are negative regulators of this nuclear receptor, making the stabilization of this protein-protein interaction (PPI) an interesting strategy. The stabilizer ( 1 ) consists of three symmetric peptidic arms containing an arginine mimetic, previously described as the GCP motif. 1 stabilizes the 14-3-3ζ/ERα interaction synergistically with the natural product Fusicoccin-A and was thus hypothesized to bind to a different site. This is supported by computational analysis of 1 binding to the binary complex of 14-3-3 and an ERα-derived phosphopeptide. Furthermore, 1 shows selectivity towards 14-3-3ζ/ERα interaction over other 14-3-3 client-derived phosphomotifs. These data provide a solid support of a new binding mode for a supramolecular 14-3-3ζ/ERα PPI stabilizer. 相似文献
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