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981.
Rosa M. Claramunt Pilar Cornago M. Dolores Santa María Verónica Torres Elena Pinilla M. Rosario Torres 《Supramolecular chemistry》2013,25(4):349-356
The X-ray structure and the solid-state NMR measurements, mainly 15N CPMAS of the labelled compound, allow to determine the static and dynamic properties of 3(5)-ethyl-5(3)-phenyl-1H-pyrazole. The compound is a tetramer formed by three 5-ethyl-3-phenyl-1H-pyrazole and one 3-ethyl-5-phenyl-1H-pyrazole tautomers in dynamic equilibrium with the complementary situation. 相似文献
982.
983.
Abstract We used canonical correlation analysis to examine the multivariate association between two distinct data sets commonly measured or calculated for approximately 600 chemicals: (1) measured or calculated values of select physieochemical properties (i.e., K ow, boiling point, heat of vaporization, molecular weight, water solubility, molecular volume, hydrogen bonding potential, and vapor pressure) and (2) calculated algorithmically-derived variables (i.e., topological and neighborhood indices derived from graph theory). Canonical correlation analysis identified eight highly significant associations between linear combinations of graph-theoretic variables and linear combinations of physicochemical properties. The set of graph theoretic variables was significantly related to all physieochemical properties, explaining 55% to 99% of the variation in these properties. 相似文献
984.
985.
We have investigated the effect of axial magnetic field on the band structure, dipole matrix elements and absorption spectrum in different energy ranges, using tight binding approximation. It is found that magnetic field breaks the degeneracy in the band structure and creates new allowed transitions in the dipole matrix which leads to creation of new peaks in the absorption spectrum. It is found that, unlike to CNTs which show metallic–semiconductor transition, the BNNTs remain semiconductor in any magnetic field strength. By calculation the diameter dependence of peak positions, we found that the positions of three first peaks in the lower energy region (E <5.3 eV) are proportional to n−2. In the middle energy region (7 < E < 7.5 eV) all (n, 0) zigzag BNNTs, with even and odd nanotube index, have two distinct peaks in the absence of magnetic field which these peaks may be used to identify zigzag BNNTs from other tube chiralities. For odd (even) tubes, in the middle energy region, applying the magnetic field leads to splitting of these two peaks into three (five) distinct peaks. 相似文献
986.
987.
Dr. Tran Quang Hung Dr. Ferial Terki Dr. Souleymane Kamara Mourad Dehbaoui Prof. Salam Charar Brajalal Sinha Prof. CheolGi Kim Dr. Philippe Gandit Il'ya A. Gural'skiy Dr. Gabor Molnar Dr. Lionel Salmon Dr. Helena J. Shepherd Dr. Azzedine Bousseksou 《Angewandte Chemie (International ed. in English)》2013,52(4):1058-1058
988.
Dr. Bing Wang Dr. De Yu Wang Dr. Zhenxiang Cheng Prof. Dr. Xiaolin Wang Prof. Dr. Yuan Xu Wang 《Chemphyschem》2013,14(6):1245-1255
Phase stability is important to the application of materials. By first‐principles calculations, we establish the phase stability of chromium borides with various stoichiometries. Moreover, the phases of CrB3 and CrB4 have been predicted by using a newly developed particle swarm optimization (PSO) algorithm. Formation enthalpy–pressure diagrams reveal that the MoB‐type structure is more energetically favorable than the TiI‐type structure for CrB. For CrB2, the WB2‐type structure is preferred at zero pressure. The predicted new phase of CrB3 belongs to the hexagonal P‐6m2 space group and it transforms into an orthorhombic phase as the pressure exceeds 93 GPa. The predicted CrB4 (space group: Pnnm) phase is more energetically favorable than the previously proposed Immm structure. The mechanical and thermodynamic stabilities of predicted CrB3 and CrB4 are verified by the calculated elastic constants and formation enthalpies. The full phonon dispersion calculations confirm the dynamic stability of WB2‐type CrB2 and predicted CrB3. The large shear moduli, large Young’s moduli, low Poisson ratios, and low bulk and shear modulus ratios of CrB4? PSC and CrB4? PSD indicate that they are potential hard materials. Analyses of Debye temperature, electronic localization function, and electronic structure provide further understanding of the chemical and physical properties of these borides. 相似文献
989.
Controlling the surface chemistry of nucleating seeds during wet‐chemical synthesis allows for the preparation of morphologically well‐defined nanostructures. Synthesis conditions play a key role in the surface properties, which directly affect the functional properties of the material. Therefore, it is important to establish post‐synthesis treatments to facilitate the optimization of surface properties with respect to a specific application, without losing the morphological peculiarity of the nanostructure. We studied the surface properties of highly crystalline and porous anatase TiO2 nanowire (NW) electrodes, grown by chemical‐bath deposition in fluoride‐containing solutions, using a combined electrochemical and spectroscopic approach. As‐deposited films showed low capacity for catechol adsorption and a poor photoelectrocatalytic activity for water oxidation. Mild thermal annealing at 200 °C resulted in a significant improvement of the electrode photoelectrocatalytic activity, whereas the bulk properties of the NWs (crystal structure, band‐gap energy) remained unchanged. Enhancement of the functional properties of the material is discussed on the basis of adsorption capacity and electronic properties. The temperature‐induced decrease of recombination centers, along with the concomitant increase of adsorption and reaction sites upon thermal annealing are called to be responsible for such improved performance. 相似文献
990.
以MoO42-部分取代Li3Fe2(PO4)3中的PO43-,研究表明:加入的MoO42-离子主要以固溶形式存在于Li3Fe2(PO4)3中,起到了显著改善其电化学性能的作用。其中,MoO42-掺杂浓度为0.3的样品表现出最佳的电化学性能,其在0.5C倍率下的首次放电容量为113.7 mAh·g-1,这一数值比未掺杂的提高了20.7%;经过60次循环充放电,容量保持率为94%。将放电倍率从0.5C逐步增大至5C,再降至初始的0.5C,并在每个倍率循环10次,这一材料的最终放电容量可达首次0.5C的95%。这些优异的性能应归因于MoO42-掺杂使材料的氧化还原能力增强,氧化还原电对的电势差减小,电池内部的电荷转移电阻减小,以及Li+扩散系数增加。 相似文献