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1.
采用基于密度泛函理论的平面波赝势方法和广义梯度近似,对未掺杂、掺B、掺N的碳纳米管(CNT)不同位置上Al原子的吸附进行了几何优化,计算了吸附Al、掺杂前后CNT的能带结构、态密度、差分电荷密度、电荷布居数和吸附能.计算结果表明,掺B使CNT形成缺电子状态,利于具有自由电子的Al原子的吸附结合,可显著提高Al在金属性的(5,5)CNT和半导性的(8,0)CNT外壁的吸附能;掺杂N形成多电子状态,在费米能级附近半满的施主能级也利于填充Al的价电子,改善Al在(5,5)CNT和(8,0)CNT外壁的吸附结合性
关键词:
密度泛函理论
单壁碳纳米管
B(N)掺杂
Al原子吸附 相似文献
2.
单壁碳纳米管吸附对三联苯的研究 总被引:1,自引:1,他引:0
利用对三联苯对单壁碳纳米管进行了化学修饰,并利用透射电镜、紫外可见吸收光谱、拉曼光谱对修饰后的单壁碳纳米管进行了表征分析.通过对比吸附前后的紫外可见吸收光谱发现,吸附后的光谱强度大约下降63.1%,说明单壁碳纳米管吸附上了对三联苯.通过拉曼光谱分析发现,吸附后单壁碳纳米管的拉曼光谱中主要峰的位置向长波方向移动了6~7 cm-1,认为拉曼光谱发生移动的原因是单壁碳纳米管吸附对三联苯前后状态的改变导致的. 相似文献
3.
采用拉伸分子动力学方法研究了单壁碳纳米管(8, 8)在室温下从硅基板上被剥离的过程.当碳纳米管(CNT)在硅基底上被剥离时, 剥离距离和理想弹簧所测平均剥离力之间呈现一定规律的关系曲线,并出现了较大的正、负峰值. 比较了不同剥离速度下的平均剥离力,并拟合了其峰值与速度的关系. 拉伸分子动力学模拟结果显示,所需剥离力的最大值与速度之间呈现一定的线性关系, 模拟结果同生物物理学上类似的剥离实验结果符合较好,但相比于高分子, CNT和硅(Si)组成的界面吸附性能更强.讨论了碳纳米管长度、 半径及缺陷对剥离过程的影响,研究表明:所需最大的剥离力与CNT的长度无关, 但随CNT半径的增加,需要的最大剥离力线性增加; 5-7-7-5缺陷对剥离力最大值影响较小,而半径变化缺陷会削减最大剥离力. 在原子尺度对未来的试验进行了理论预测,为碳纳米管在硅微电子工业中的应用提供了理论基础. 相似文献
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碳纳米管(CNT)对于气体有超强的敏感性,可用于制备基于CNT的有害气体传感器.本文采用基于密度泛函理论的第一性原理研究Au掺杂CNT对NO和O_2的吸附特性.对吸附能、最终吸附距离、电荷转移量、态密度等的分析显示,Au掺杂使得CNT与NO间的交互作用明显增强,其中N原子端靠近CNT交互作用更强.禁带宽度和电荷密度分析表明,相比于NO分子中O原子端或者O2吸附,NO分子中N原子端与CNT发生交互作用会使体系导电性变化更为明显.说明Au掺杂能够很好地屏蔽空气中O_2对CNT导电性的影响,Au掺杂CNT作为NO气敏材料是可行的. 相似文献
6.
单壁碳纳米管吸附酞菁类有机物的研究 总被引:1,自引:0,他引:1
利用苯氧基酞菁修饰单壁碳纳米管,并利用透射电子显微镜、紫外可见吸收光谱、荧光光谱以及拉曼光谱进行了表征分析.在透射电镜下观察到结合物呈现糖葫芦状,吸附后吸收光谱以及荧光光谱中峰的强度明显下降说明单壁碳纳米管吸附了大量的苯氧基酞菁,通过拉曼光谱发现吸附后单壁碳纳米管的拉曼光谱中主要峰的位置向长波数方向移动,原因是单壁碳纳米管吸附苯氧基酞菁前后状态的改变导致的. 相似文献
7.
将修正的分子结构力学方法(MMSMM)扩展用来分析单壁碳纳米管的动态特性. 应用MMSMM方法分析了悬臂单壁碳纳米管的振动特性,对计算得到的单壁碳纳米管振动的基频进行了讨论. 发现单壁碳纳米管振动的基频与碳管的直径和长度有关,呈现出一定的尺度依赖性,当管径很小的时候,单壁碳纳米管的振动基频可以达到GHz.并尝试用有限元方法模拟碳管的振动问题. 两种方法得到的结果表明,在常用的原子模拟方法(如分子动力学方法)解决碳纳米管振动问题遇到困难时,通过扩展修正可以简单的处理这类问题,并可以保持很好的精度. 相似文献
8.
卷曲和管径对单壁碳纳米管π轨道取向的影响 总被引:6,自引:3,他引:3
由于卷曲效应,单壁碳纳米管中π轨道的取向不再和石墨一样与三个σ键垂直,也不沿管的径向,而是与径向发生一定小角度的倾斜.π轨道的取向与单壁碳纳米管的管径和曲率有密切的关系.本文从几何结构出发,计算了(n,0),(n,n)和(n,m)三种单壁碳纳米管π轨道的倾角.结果表明三种倾角是不完全相同的. 相似文献
9.
本文利用密度泛函理论研究了Rh原子在(6,6)单壁碳纳米管内外的吸附行为. 通过对Rh在单壁碳纳米管上不同吸附位的吸附构型与吸附能的研究发现: Rh吸附在管内、外的洞位最稳定, 且管外吸附比在管内强. 这是由于单壁碳纳米管的卷曲效应使得管外电荷密度比管内大造成的. 态密度分析表明, 吸附在管内外的Rh原子的5s电子均转移到了4d轨道上; Rh原子4d轨道上的电子转移到了(6, 6)碳管上, 使Rh带正电, 碳管带负电. 结合能带分析表明, Rh原子吸附在管内磁性较弱, 而吸附在管外较强.
关键词:
密度泛函理论
单壁碳纳米管
Rh原子
吸附 相似文献
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The hydrogen chemical adsorption on a single-walled carbon nanotube (6, 6) has been studied by quantum-chemical computer simulation. Different variants of hydrogen coverage of the nanotube have been considered, and the dependences of the adsorption energy and the nanotube strain energy on the coverage density have been found. In addition, the adsorption has been considered on both the outer and inner surfaces of the nanotube wall. It has been established that some adsorption conformations are unstable, which leads to fracture of the nanotubes. 相似文献
12.
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
13.
Luoxin Wang Changhai Yi Hantao Zou Houlei Gan Jie Xu Weilin Xu 《Molecular physics》2013,111(14):1841-1849
The non-covalent adsorption of the insensitive explosive TATB (1,3,5-triamino-2,4,6-trinitrobenzene) on the sidewalls of single-walled carbon nanotubes (CNTs) has been calculated using an ONIOM approach. It was found that TATB deformed remarkably when attached non-covalently on the surface of CNTs, especially on the inner wall of the nanotubes. The diameter of the nanotube determined the degree of distortion of the inner-adsorbed TATB, but had little effect on the deformation of the outer-attached TATB. The non-covalent combination of TATB with the nanotube is an exothermic process due to the negative adsorption energy. TATB adsorption on the inner wall of nanotubes was energetically more favorable than that on the outer wall of the nanotubes. In both cases, the adsorption became more stable with increasing diameter of the nanotube. Our theoretical results can be used as a guideline for the design of energetic nanocomposites based on CNTs and aromatic nitro-explosives. 相似文献
14.
Nowadays, carbon nanotubes (CNT) play an important role in practical applications in fluidic devices. To this end, researchers have studied various aspects of vibration analysis of a behavior of CNT conveying fluid. In this paper, based on nonlocal elasticity theory, single-walled carbon nanotube (SWCNT) is simulated. To investigate and analyze the effect of internal fluid flow on the longitudinal vibration and stability of SWCNT, the equation of motion for longitudinal vibration is obtained by using Navier-Stokes equations. In the governing equation of motion, the interaction of fluid-structure, dynamic and fluid flow velocity along the axial coordinate of the nanotube and the nano-scale effect of the structure are considered. To solve the nonlocal longitudinal vibration equation, the approximate Galerkin method is employed and appropriate simply supported boundary conditions are applied. The results show that the axial vibrations of the nanotubesstrongly depend on the small-size effect. In addition, the fluid flowing in nanotube causes a decrease in the natural frequency of the system. It is obvious that the system natural frequencies reach zero at lower critical flow velocities as the wave number increases. Moreover, the critical flow velocity decreases as the nonlocal parameter increases. 相似文献
15.
We report the results of our first-principles study based on density functional theory on the interaction of alkanethiols with both defected and defect-free single-walled carbon nanotube (SWCNT). The adsorption energies are calculated for various configurations such as alkanethiol molecule approaching to defect sites heptagon, hexagon, and pentagon in defective tube, and another case where the alkanethiol approaching to hexagon in defect-free nanotube. The calculated results showed that alkanethiols are rather strongly bound to the outer surface of both the defected and defect-free carbon nanotubes with the binding energy of about −50.58 kcal/mol, consistent with the experimental result. We also find that alkanethiols prefer to be adsorbed on the hexagon ring site of defect-free nanotube. Furthermore, the effect of alkanethiols chain length on the adsorption of alkanethiols on carbon nanotubes has been investigated, and the obtained results reveal that the longer alkanethiols bind rather more strongly to the nanotube surface. 相似文献
16.
X. Y. Liu W. G. Sun C. Y. Wang Y. J. Tang 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2010,56(3):341-345
The physisorption of molecular hydrogen in BC3 composite single-walled nanotube, investigated using density functional
theory, was compared with single-walled carbon nanotube. Both external and
internal adsorption sites of these two nanotubes have been studied with the
hydrogen molecular axis oriented parallel to the nanotube wall. The
calculated results show that: ([see full textsee full text]) the physisorption energies of a H2
molecule are larger for BC3(8,0) composite nanotube than for C(8,0)
nanotube at all adsorption sites examined. ([see full textsee full text]) For these two nanotubes, the
physisorption energies are larger for hydrogen bound inside the nanotubes
than for adsorption outside the nanotubes. The different behavior between
these two nanotubes is explained by the contour plots of electron density
and charge-density difference of them. The present computations suggest that
BC3 nanotube may be a better candidate for hydrogen storage than carbon
nanotube. 相似文献
17.
Molecular dynamics (MD) simulations were performed to provide an insight about the molecule distribution and thermophysical properties of n-heptacosane confined in the (25, 25) single-walled carbon nanotube (CNT). The results show that an orderly distribution of n-heptacosane molecules along the CNT inner wall is clearly observed. Meanwhile, n-heptacosane confined in CNT exhibits an increased self-diffusion coefficient, a decreased melting point and an enhanced thermal conductivity, compared to the bulk. The simulations reveal that MD is an effective and convenient method to understand the variation characteristics of alkane-based phase change materials confined in CNT on molecular and atomic scale. 相似文献
18.
Jeffrey J. LombardoWilson K.S. Chiu 《Applied Surface Science》2011,257(14):5931-5937
As the mechanisms of carbon nanotube (CNT) growth becomes known, it becomes important to understand how to implement this knowledge into reactor scale models to optimize CNT growth. In past work, we have reported fundamental mechanisms and competing deposition regimes that dictate single wall carbon nanotube growth. In this study, we will further explore the growth of carbon nanotubes with multiple walls. A tube flow chemical vapor deposition reactor is simulated using the commercial software package COMSOL, and considered the growth of single- and multi-walled carbon nanotubes. It was found that the limiting reaction processes for multi-walled carbon nanotubes change at different temperatures than the single walled carbon nanotubes and it was shown that the reactions directly governing CNT growth are a limiting process over certain parameters. This work shows that the optimum conditions for CNT growth are dependent on temperature, chemical concentration, and the number of nanotube walls. Optimal reactor conditions have been identified as defined by (1) a critical inlet methane concentration that results in hydrogen abstraction limited versus hydrocarbon adsorption limited reaction kinetic regime, and (2) activation energy of reaction for a given reactor temperature and inlet methane concentration. Successful optimization of a CNT growth processes requires taking all of those variables into account. 相似文献
19.
Dependence of the electrical properties of defective single-walled carbon nanotubes on the vacancy density 下载免费PDF全文
The relationship between the electric properties and the vacancy density in single-walled carbon nanotubes has been investigated from first principles as well as the dependence of the influencing range of a vacancy in the nanotube on the nanotube chirality.Compared with the long-range interaction of the vacancies in a single-walled carbon nanotube with non-zero chiral angle,a much shorter interaction was found between vacancies in a zigzag single-walled carbon nanotube.In this study,we investigated the bandstructure fluctuations caused by the nanotube strain,which depends on both the vacancy density and the tube chirality.These theoretical results provide new insight to understand the relationship between the local deformation of a defective single-walled carbon nanotube and its measurable electronic properties. 相似文献
20.
The thermal conductivity and diffusion behaviour of lauric acid (LA) confined in single-walled carbon nanotube (CNT) with the filling ratio of 80% are investigated by molecular dynamics (MD) simulations. It is found that the concentric multilayer LA tubes are clearly observed under the interaction of CNT and LA and the hydrogen bonds (HB) among LA molecules in a confined environment. Due to the phonon scattering in low-frequency and the high-thermal conductivity characteristics of CNT, the axial thermal conductivity of CNT/LA is 49–57% lower than that of empty CNT and 115–188 times higher than that of crystal LA at the temperature range of 280 and 360?K. The confined LA molecules move as a whole cluster due to the long-lasting HB action and travel much faster than the bulk. 相似文献