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Density functional theory (DFT) calculations are used to study the strength of the CH…O H‐bond in the proton transfer reaction of glycine. Comparison has been made between four proton transfer reactions (ZW1, ZW2, ZW3, SCRFZW) in glycine. The structural parameters of the zwitterionic, transition, and neutral states of glycine are strongly perturbed when the proton transfer takes place. It has been found that the interaction of water molecule at the side chain of glycine is high in the transition state, whereas it is low in the zwitterionic and neutral states. This strongest multiple hydrogen bond interaction in the transition state reduces the barrier for the proton transfer reaction. The natural bond orbital analysis have also been carried out for the ZW2 reaction path, it has been concluded that the amount of charge transfer between the neighboring atoms will decide the strength of H‐bond. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2006 相似文献
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María Abreu-Sepúlveda Dominique E. Williams Ashfia Huq Chetan Dhital Yunchao Li M. Parans Paranthaman Karim Zaghib A. Manivannan 《Ionics》2016,22(3):317-325
Titanium, tantalum-substituted Li7La3Zr2-xAxO12 (LLZO, A?=?Ta, Ti) garnets, and chromium-substituted La(2/3)-xLi3xTi1-yCryO3 (LLTO) perovskites were prepared by a conventional solid-state reaction and the Pechini processes. The desired crystal phases were obtained by varying the calcination temperature and time, as well as the substitution concentration. All samples indicated decomposition of the precursors when heated above 750 °C and formation of the desired phase after heat treatment at higher temperatures. Neutron diffraction data shows the formation of a predominant cubic phase in the case of Ta-LLZO, and monoclinic phase with minor impurity phases for Cr-LLTO. Ionic conductivity for Ti-LLZO (Li7La3Zr1.4Ti0.6O12), Ta-LLZO (Li6.03La3Zr1.533Ta0.46O12), and Cr-LLTO (La(2/3)-xLi3xTi0.9Cr0.1O3) at room temperature were found to be 5.21?×?10?6, 1.01?×?10?6, and 1.2?×?10?4 S cm?1, respectively. The activation energies of the compounds were determined from the Arrhenius plot and were 0.44 eV (Ti0.6-LLZO), 0.54 eV (Ta0.5-LLZO), and 0.20 eV (Cr0.1-LLTO). 相似文献
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Journal of Structural Chemistry - The structure and metal complexation studies using dispersion-corrected density functional theory methods are performed for four stable glycolic acid conformers... 相似文献
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W. Hoffmann H. Breitzke C. T. Simmons K. Lüders G. Buntkowsky H. H. Limbach E. V. Antipov A. A. Gippius O. Loebich H. R. Khan M. Paranthaman J. R. Thompson 《Applied magnetic resonance》1995,8(1):57-65
Hg-oxide ceramic high temperature superconductors were studied by199Hg and63,65Cu NMR spectroscopy. Room temperature spectra, spin-spin and spin-lattice relaxation times of samples with different superconducting transition temperatures are presented. A spin-lattice relaxation time ofT 1=35 msec and a spin-spin relaxation time ofT 2=1.6 msec were found for the199Hg NMR. All samples exhibit similar characteristic powder spectra caused by an axially symmetric199Hg spin interaction. The isotropic value and the anisotropy of the tensor relative to solid HgCl2 as a standard substance is estimated. Furthermore, results of63,65Cu NMR measurements at a temperature of 4.2 K which exhibit a typical powder line shape (forI=3/2) are presented. 相似文献
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Reactivity of molecular oxygen with aluminum clusters: Density functional and Ab Initio molecular dynamics simulation study 下载免费PDF全文
Selvarengan Paranthaman Jiwon Moon Kiryong Hong Jeongho Kim Dong Eon Kim Joonghan Kim Tae Kyu Kim 《International journal of quantum chemistry》2016,116(7):547-554
Dissociative adsorption of molecular oxygen (O2) on aluminum (Al) clusters has attracted much interest in the field of surface science and catalysis, but theoretical predictions of the reactivity of this reaction in terms of barrier height is still challenging. In this regard, we systematically investigate the reactivity of O2 with Al clusters using density functional theory (DFT) and atom‐centered density matrix propagation (ADMP) simulations. We also calculate potential energy surfaces (PESs) of the reaction between O2 and Al clusters to estimate the barrier energy of this reaction. The M06‐2X functional gives the barrier energy in agreement with the one calculated by coupled cluster singles and doubles with perturbed triples (CCSD(T)) while the TPSSh functional significantly underestimates the barrier height. The ADMP simulation using the M06‐2X functional predicts the reactivity of O2 with the Al cluster in agreement with the experimental findings, that is, singlet O2 readily reacts with Al clusters but triplet O2 is less reactive. We found that the ability of a DFT functional to describe the charge transfer appropriately is critical for calculating the barrier energy and the reactivity of the reaction of O2 with Al clusters. The M06‐2X functional is relevant for investigating chemical reactions involving Al and O2. © 2016 Wiley Periodicals, Inc. 相似文献
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C.A. Bridges A.S. Sefat L. Cranswick M.P. Paranthaman 《Journal of solid state chemistry》2011,184(4):830-842
The influence of Bi3+ on the structural and magnetic properties of the rare-earth-containing perovskites REFe0.5Mn0.5O3 (RE=La,Nd) was studied, and the limit of bismuth substitution was determined to be x≤0.5 in BixRE1−xFe0.5Mn0.5O3+δ (RE=La,Nd) at ambient pressure. Crystal structures in both La and Nd series were determined to be GdFeO3-type Pnma with the exception of the Bi0.3La0.7Fe0.5Mn0.5O3 sample, which is monoclinic I2/a in the a−b−b− tilt scheme. The samples undergo a transition to G-type antiferromagnetic order along with a weak ferromagnetic component, mixed with cluster-glass type behavior. The substitution of bismuth into the lattice results in a drop in TN relative to the lanthanide end-members. Long range ordering temperatures TN in the range 240-255 K were observed, with a significantly lower ordered magnetic moment in the case of lanthanum (M∼1.7-1.9 μB) than in the case of neodymium (M∼2.1 μB). 相似文献
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C.A. Bridges V.V. Krishnamurthy S. Poulton M.P. Paranthaman B.C. Sales C. Myers S. Bobev 《Journal of magnetism and magnetic materials》2009,321(22):3653-3657
This paper reports a neutron powder diffraction study of CaMn2Sb2 in the temperature range of 20–300 K. Collinear long-range antiferromagnetic order of manganese ions occurs below 85 K, where a transition is observed in the dc magnetic susceptibility measured with a single crystal. Short-range magnetic order, characterized by a broad diffraction peak corresponding to a d-spacing of approximately 4 Å (2θ≈22°), is also observed above 20 K. The long-range antiferromagnetic order is indexed by the chemical unit cell, indicating a propagation vector k=(0 0 0), with a refined magnetic moment of 3.38 μB at 20 K. Two possible magnetic models have been identified, which differ in spin orientation for the two manganese ions with respect to the ab plane. The model with spins oriented at a 25±2° angle relative to the ab plane gives an improved fit compared to the other model in which the spins are constrained to the ab plane. Representational analysis can account for a model involving a c-axis component only by the mixing of two irreducible representations. 相似文献
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A superhydrophobic surface was obtained by embedding hydrophobically modified fumed silica (HMFS) particles in polyvinylidene fluoride (PVDF) matrix. The water contact angle (WCA) on the PVDF-HMFS hybrid composite coating is influenced by the content and nature of silica particles in the coating. As the silica concentration in PVDF matrix was increased from 33.3% to 71.4%, WCA increased from 117° to 168° and the sliding angle decreased from 90° to <1°. Surface topography of the coating was examined using scanning electron microscopy. An irregular rough surface structure composed of microcavities and nanofilaments was found to be responsible for the superhydrophobicity. The method is simple and cost-effective and can be used for preparing self-cleaning superhydrophobic coating on large areas of different substrates. 相似文献
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