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相互作用势对模拟计算单壁碳纳米管物理吸附储氢的影响 总被引:9,自引:4,他引:5
采用巨正则Monte Carlo方法模拟氢分子在单壁碳纳米管中的储存与分布,重点研究了Lennard-Jones势、Crowell-Brown势和Silvera- Goldman势对模拟计算单壁碳纳米管物理吸附储氢的影响.计算结果显示,碳纳米管与氢分子间的相互作用宜采用Lennard-Jones势描述;氢分子与氢分子间相互作用的描述则与碳纳米管的管径有关,管径较小时选Lennard-Jones势较佳,管径偏大时取七参数Silvera-Goldman 势更为合理,而三参数Silvera-Goldman势则不宜采用;并给出了相应的理论解释. 相似文献
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分子内的电子-振动耦合特性对电子跃迁和分子光谱特征有重要影响,是分子光谱学研究的中心课题之一.本文利用具有亚纳米分辨的扫描隧道显微镜诱导发光成像技术,通过高度局域的隧穿电子来充电激发单个苝四甲酸二酐分子,研究该分子的瞬时带电态(–2价态)的电致发光特性以及相应的电子-振动跃迁的实空间成像特征.具有亚分子分辨的光谱成像结果表明, 0-0纯电子跃迁的光子图“两点”亮斑特征是沿分子短轴的,而某些电子振动峰的光子图“两点”亮斑方向却沿着分子长轴,相对于0-0跃迁光子图的图案旋转了90°.这表明这些振动态所对应的跃迁偶极取向是沿着分子长轴的,相对于0-0的纯电子跃迁的偶极取向发生了明显的变化,说明这些分子振动模式在电子的跃迁过程中对电子态空间分布产生了重要扰动.理论计算表明,这种跃迁偶极的变化源自于与Herzberg-Teller贡献相关的电子-振动耦合.反对称的振动模式对纯电子跃迁的跃迁密度、特别是具有较大跃迁密度的原子产生了强烈的动态扰动,或者说对分子波函数进行了“整形手术”,从而诱导出沿分子长轴方向的跃迁电荷振荡,引发沿分子长轴的跃迁偶极.本文结果为从实空间的视角来直观理解分子瞬时带电态中... 相似文献
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一维、二维、三维氢原子能级和电子分布概率 总被引:1,自引:0,他引:1
通过一维、二维氢原子定态薛定谔方程的严格解得出的能级公式和波函数,分析了一维、二维氢原子能级特点、简并度和电子分布概率,并将它们与三维氢原子进行比较,发现一维、二维、三维氢原子能级和电子分布概率有许多不同之处。 相似文献
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本文在一级Bom近似下,研究了激光场中正电子对基态氢原子的碰撞电离反应,并与入射粒子为电子的(e,2e)反应进行了对比.激光场中正电子态和敲出电子态分别采用Volkov波函数和Coulomb-Volkov波函数,靶原子的缀饰波函数由含时微扰论给出.计算结果显示激光缀饰的三重电离截面明显依赖于入射粒子电荷符号.激光越强,二者差距越大. 相似文献
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The collective dynamic behavior of carbon atoms of a (17, 0) zigzag single wall carbon nanotube is investigated under tensile strains by molecular dynamics (MD) simulations. The “slip vector” parameter is used to study the collective motion of a group of atoms and the deformation behavior in three different directions (axial, radial, and tangential) of a (17, 0) carbon nanotube. The variations of radial slip vectors indicate almost all carbon atoms of the (17, 0) carbon nanotube will stay on the cylindrical surface before the yielding of the single wall carbon nanotube (SWNT). Furthermore, the tangential vectors show kinking deformation for the (17, 0) zigzag tube only rarely appears when the crack occurs. Non-symmetrical deformation around a carbon atom along the axial direction also can be found. The variations in the slip vector values of each atom display a symmetrical crack along the horizontal direction and normal to the tube axis. Chain-like structures with 3–4 atoms can be observed, with the number of chain-like structures decreasing before the breakage of the SWNT. The mechanical properties and dynamic behavior of a (17, 0) zigzag SWNT under tensile strain are also compared with that of a (10, 10) armchair tube in our previous study (Weng et al. 2009). 相似文献
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Seifollah Jalili Arezou Jaberi Mohammad Ghasem Mahjani Majid Jafarian 《Molecular physics》2013,111(6):361-368
Utilising molecular dynamics simulations, the hydrogen molecules adsorption isotherms of the (8,?0) palladium decorated single-walled carbon nanotube (SWNT) were obtained. The hydrogen adsorption was studied on the external, interstial and internal surfaces of the SWNT bundle at several temperatures ranging from 77 to 400?K. The results were compared with the bare single-walled carbon nanotube bundle under the same conditions. The decorated carbon nanotube bundle hydrogen adsorption was significantly higher than that of the bare one. The hydrogen desorption and readsorption were studied using temperature as the readsorption/desorption variable. The rate constants were calculated for the hydrogen desorption at different temperatures. The calculated decorated SWNT bundle hydrogen desorption activation energy was higher than that for the bare SWNT bundle. The calculated activation energies for the hydrogen desorption in both nanotube bundles specified the temperature dependency of hydrogen desorption. 相似文献
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采用密度泛函方法对铜原子在有限长(5,5)椅型单壁碳纳米管的吸附行为进行了研究.计算结果表明,铜原子吸附在管外壁要比吸附在管内壁能量上更为有利,在管外壁碳原子顶位吸附最佳,属于明显的化学吸附.且用前线轨道理论对其成键特性进行了分析,表明在顶位吸附时主要由铜原子的4s轨道电子与碳纳米管中耦合的σ-π键形成新的σ键.此外还对比计算了两种典型位置电子密度,发现顶位吸附的成键中有更大的电子云重叠.进一步表明在某些情况下铜碳原子可以成键.
关键词:
碳纳米管
铜原子
成键特性 相似文献
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We have calculated the quantum conductance of single-walled
carbon nanotube (SWNT) waveguide by using a tight binding-based
Greens function approach. Our calculations show that the slow
conductance oscillations as well as the fast conductance
oscillations are manifestations of the intrinsic quantum
interference properties of the conducting SWNTs, being independent
of the defect and disorder of the SWNTs. And zigzag type tubes do
not show the slow oscillations. The SWNT electron waveguide is
also found to have distinctly different transport behavior
depending on whether or not the length of the tube is commensurate
with a (3N+1) rule, with N the number of basic carbon repeat
units along the nanotube length. 相似文献
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Nikos Tagmatarchis Maurizio Prato Dirk M. Guldi 《Physica E: Low-dimensional Systems and Nanostructures》2005,29(3-4):546
Soluble carbon nanotube ensembles having ferrocene units covalently introduced by 1,3-dipolar cycloaddition of azomethine ylides have been synthesized and studied for light-induced electron transfer interactions. Additionally, supramolecular means have been utilized to immobilize a positively charged water-soluble pyrene derivative to purified single-walled carbon nanotube (SWNT), which was further coupled by attractive electrostatic interactions to an oligoanionic porphyrin. Electron transfer from the photoexcited states were probed by fluorescence and transient absorption spectroscopy measurements. 相似文献
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DNA self-assembled hybrid nanostructures are widely used in recent research in nanobiotechnology. Combination of DNA with carbon based nanoparticles such as single-walled carbon nanotube (SWNT), multi-walled carbon nanotube (MWNT) and carbon quantum dot were applied in important biological applications. Many examples of biosensors, nanowires and nanoelectronic devices, nanomachine and drug delivery systems are fabricated by these hybrid nanostructures. In this study, a new hybrid nanostructure has been fabricated by noncovalent interactions between single or double stranded DNA and SWNT nanoparticles and biophysical properties of these structures were studied comparatively. Biophysical properties of hybrid nanostructures studied by circular dichroism, UV–vis and fluorescence spectroscopy techniques. Also, electrochemical properties studied by cyclic voltammetry, linear sweep voltammetry, square wave voltammetry, choronoamperometry and impedance spectroscopy (EIS). Results revealed that the biophysical and electrochemical properties of SWNT/DNA hybrid nanostructures were different compare to ss-DNA, ds-DNA and SWNT singly. Circular dichroism results showed that ss-DNA wrapped around the nanotubes through π-π stacking interactions. The results indicated that after adding SWNT to ss-DNA and ds-DNA intensity of CD and UV–vis spectrum peaks were decreased. Electrochemical experiments indicated that the modification of single-walled carbon nanotubes by ss-DNA improves the electron transfer rate of hybrid nanostructures. It was demonstrated SWNT/DNA hybrid nanostructures should be a good electroactive nanostructure that can be used for electrochemical detection or sensing. 相似文献
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S. Friedrichs R. R. Meyer J. Sloan A. I. Kirkland J. L. Hutchison M. L. H. Green 《Physics of the Solid State》2002,44(3):463-466
The detailed inclusion crystallography of a one-dimensional valentinite Sb2O3 crystal incorporated within a helical (21, ?8) single-walled carbon nanotube (SWNT) was identified from a phase image that was recovered via a modified object wave restoration scheme. A detailed analysis of asymmetric fringe contrast in the tube walls provided strong evidence for the chiral sense of the tube itself. Due to the good agreement of the observed wall periodicity with the determined absolute focus values and power spectra obtained from single-pixel line traces along both tube walls, we were able to determine the chiral sense of the SWNT and the tilt angle of the Sb2O3/SWNT composite relative to the electron beam. The angle between the optimum $\left\langle {10\bar 1} \right\rangle $ viewing direction of the crystal fraction and the tube axis, which is aligned with the $\left\langle {4\bar 12} \right\rangle $ direction of the Sb2O3 crystal, is 78.3°. Since small deviations from this viewing direction make an insignificant difference to the observed contrast, a tube inclination of 15° is plausible for both the Sb2O3 crystal and the assigned (21, ?8) SWNT, which is the mirror image of a (13, 8) SWNT. 相似文献
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We present classical molecular dynamics simulations demonstrating that single-wall carbon nanotube (SWNT) bundles collapse under hydrostatic pressure. The collapse pressures obtained as a function of nanotube diameter are in excellent quantitative agreement with new data presented here for small diameter (d approximately 0.8 nm) SWNTs, and the majority of previously published results, although there remain some unreconciled contradictions in the literature. The collapse pressure is found to be independent of the nanotube chirality, and a lower limit on the largest SWNT that remains inflated at atmospheric pressure is established (d>4.16 nm). 相似文献
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In this paper, based on the tight-binding Hamiltonian model and within the framework of a generalized Green’s function technique,
the electronic conduction through the poly(GACT)-poly(CTGA) DNA molecule in SWNT/DNA/SWNT structure has been numerically investigated.
In a ladder model, we consider DNA as a planar molecule containing M cells and four further sites (two base pair sites and two backbone sites) in each cell, sandwiched between two semi-infinite
single-walled carbon nanotubes (SWNT) as the electrodes. Having relied on Landauer formalism, we focussed on studying the
current-voltage characteristics of DNA, the effect of the coupling strength of SWNT/DNA interface and the role of tube radius
of nanotube contacts on the electronic transmission through the foregoing structure. Finally, a characteristic time was calculated
for the electron transmission, which measures the delay caused by the tunnelling through the SWNT/DNA interface. The results
clearly show that the calculated characteristic time and also the conductance of the system are sensitive to the coupling
strength between DNA molecule and nanotube contacts. 相似文献
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Hongjun Jing Yadong Jiang Xiaosong Du Huiling Tai Guangzhong Xie 《Applied Physics A: Materials Science & Processing》2012,109(1):111-118
Poly(diallyldimethylammonium chloride)/single-walled carbon nanotube (PDDA/SWNT) multilayered thin films were prepared on quartz crystal microbalance by layer-by-layer self-assembly technique, and their sensing properties to humidity were studied. The SWNTs were characterized by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. The composite films were observed by field-emission scanning electron microscope. Two types of SWNT humidity sensors were fabricated using SWNTs and carboxyl (COOH) modified SWNTs as sensitive material, respectively. The results showed that the sensitivity of the PDDA/SWNT?CCOOH humidity sensor was 20.23?% higher than that of the PDDA/SWNT sensor. In contrast, the latter had a much superior hysteresis property, and the reason to cause this phenomenon was discussed. 相似文献