共查询到19条相似文献,搜索用时 578 毫秒
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采用分子动力学模拟方法研究了硅纳米颗粒在碳纳米管上的生长,并分析了这种复合材料的基本结构.研究表明,由于硅原子和碳纳米管之间的相互作用以及碳纳米管的巨大的表面曲率,硅原子在碳纳米管表面不是形成覆盖碳纳米管的二维薄膜,而是生成具有三维结构的硅纳米颗粒.小纳米颗粒的结构和无基底条件下生成的颗粒结构基本一致.对于大纳米颗粒,不同于无基底条件下形成的球状纳米晶体硅结构,硅纳米颗粒沿管轴方向伸长,其结构为类似于硅晶体的无定形网络结构.
关键词:
纳米颗粒
碳纳米管
硅
分子动力学模拟 相似文献
3.
利用分子动力学方法研究了碳纳米管表面硅颗粒的结构和热稳定性.发现随着温度的增加,碳纳米管表面硅颗粒结构发生了由笼状结构到帐篷状结构的变化.碳管表面的硅颗粒在熔点附近或更高的温度下,结构变得无序,并沿着碳纳米管轴向方向伸长.此外,通过对比分析碳纳米管表面硅颗粒与自由条件下硅颗粒Lindemann指数的变化,发现碳纳米管表面的硅纳米颗粒熔点要低于自由条件下硅纳米颗粒的熔点. 相似文献
4.
利用分子动力学模拟方法,研究了单壁碳纳米管与Au电极的高温熔接. 模拟结果表明,用端口吸附了Au团簇的碳纳米管在高温下能很好地与Au电极熔接. 首先将Au团簇放置于碳纳米管开口处进行高温退火,退火温度在1100 K左右,Au团簇部分Au原子进入碳纳米管管内,吸入碳纳米管中的Au原子形成壳层螺旋结构的Au纳米线,管外Au团簇呈无定形结构. 然后将吸附了Au团簇的碳纳米管与Au电极进行熔接,高温退火后,碳纳米管与Au电极表面之间形成了稳固的熔接,熔接最佳温度在800 K左右.
关键词:
碳纳米管
金电极
分子动力学模拟 相似文献
5.
本文采用分子动力学模拟方法研究了Si表面间单壁水平碳纳米管束SWCNT (10,10)的变形和摩擦特性.系统在弛豫平衡后,首先对碳纳米管束施加压力至碳纳米管或Si表面结构破坏.之后在无压力和高压力两种情况下使上表面沿水平方向做剪切运动以研究碳纳米管束的摩擦特性.结果表明,由于碳纳米管的柔韧性,碳纳米管束在加载过程中出现明显变形,但直至3.8 GPa高压下并无结构破坏.系统无压力时SWCNT (10,10)在原地轻微随机滚动,压力为3.8 GPa时,碳纳米管束出现了整体的轻微滑动,同时伴随无规律的轻微滚动,
关键词:
碳纳米管束
摩擦
分子动力学模拟 相似文献
6.
采用分子动力学方法模拟了半径从0.3–1.3 nm变化的小尺寸铝纳米团簇的熔化、凝固行为. 基于势能-温度曲线、热容-温度曲线分析, 获得了熔点、凝固点与尺寸的依变关系, 并利用表面能理论、小尺寸效应开展了现象分析.研究表明, 铝团簇原子数小于80时, 熔点和凝固点的尺寸依赖性出现无规律的异常变化; 而大于该原子数, 熔、凝固点则随着团簇尺寸的减小而单调下降; 当原子数为27时, 团簇熔点高于块材熔点近40 K. 同时, 铝纳米团簇呈现出凝固滞后现象, 即凝固点低于熔点.
关键词:
纳米团簇
熔点
凝固点
分子动力学 相似文献
7.
纳米颗粒在纳米医药、细胞成像等领域有着非常广泛的应用,深入理解纳米颗粒与生物膜之间相互作用的微观机制是纳米颗粒合成与应用的重要基础.本文采用粗粒化分子动力学模拟的方法研究了带电配体包裹的金纳米颗粒与相分离的带电生物膜之间的相互作用.结果表明,通过改变金纳米颗粒表面的配体密度、配体带电种类和比例,以及膜内带电脂分子的种类,可以方便地调控纳米颗粒在膜表面或膜内停留的位置和状态.进一步从自由能的角度分析了带电纳米颗粒与带电生物膜之间相互作用的微观物理机制.本文对纳米粒子在纳米医药、细胞成像等领域的应用具有一定的理论参考意义. 相似文献
8.
针对分子动力学模拟中碳纳米管的结构优化问题,提出了一种新的优化算法.新的优化算法在遗传算法的基础上,引入了克隆选择机理和模拟退火技术.对五个典型函数的优化测试结果表明,该算法搜索过程稳定性好,可较好地实现全局最优.将其应用于碳纳米管原子结构优化,加快了能量优化速度,提高了优化质量.模拟结果说明,混合遗传算法的优化时间随原子数增加而呈线性增长.在碳纳米管原子数较多时,结构优化时间比共轭梯度法降低一个数量级左右,大大降低了系统的模拟时间.
关键词:
分子动力学
碳纳米管
能量优化
遗传算法
克隆选择算法 相似文献
9.
基于非平衡态分子动力学模拟方法,研究了自由分子区内纳米颗粒的热泳特性.理论研究表明,纳米颗粒与周围气体分子之间的非刚体碰撞效应会明显地改变其热泳特性,经典的Waldmann热泳理论并不适用,但尚未有定量的直接验证.模拟计算结果表明:对于纳米颗粒而言,当气-固相互作用势能较弱或气体温度较高时,气体分子与纳米颗粒之间的非刚体碰撞效应可以忽略,Waldmann热泳理论与分子动力学模拟结果吻合较好;当气-固相互作用势能较强或气体温度较低时,非刚体碰撞效应较为明显,Waldmann热泳理论与模拟结果存在较大误差.基于分子动力学模拟结果,对纳米颗粒的等效粒径进行了修正,并考虑了气体分子与纳米颗粒之间的非刚体碰撞效应,理论计算结果与分子动力学模拟结果吻合较好. 相似文献
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Vladimir V. Tatarchuk Anastasiya P. Sergievskaya Irina A. Druzhinina Vladimir I. Zaikovsky 《Journal of nanoparticle research》2011,13(10):4997-5007
The kinetics of the growth of gold nanoparticles during the reduction of tetrachloroauric acid by hydrazine in dispersed aqueous
solution encapsulated by reverse micelles of Triton N-42 surfactant (with decane as dispersion medium) was studied by means
of spectrophotometry. According to DLS data, at a set value of solubilization capacity V
s/V
o = 0.005 initial micelles have an aqueous core hydrodynamic diameter d
c = 3.6±0.2 nm. The final particles obtained after full reduction of AuIII have a metallic core of defect-free single-crystalline gold with a narrow size distribution and average core diameter d
Au = 7.7 ± 1.4 nm as shown by TEM. The rate of the particle growth is limited by the rate of gold reduction. The process kinetics
corresponds to the model consisting of two stages of reduction AuIII → AuI → Au0. The stages involve the formation and redox decay of the intermediate complexes Au(N2H4)Cl3 and Au(N2H4)Cl, and each stage proceeds via two routes: (1) homogeneous in the dispersed aqueous phase, and (2) heterogeneous on the
particle surfaces. Reactions taking route (2) are autocatalytic because they proceed with participation of the surface atoms
of particles as the final products of AuIII reduction. The dependencies of observed rate constants on reagent concentrations, temperature, and solubilization capacity
of the micellar solution are studied. 相似文献
12.
M. Yamada H. Nishihara 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,24(1-3):257-260
Biferrocene-modified gold nanoparticles
(Aun-BFc) comprising 1.7, 2.2 and 2.9 nm
in average core diameter, d,
were synthesized by a substitution reaction of octyl
thiolate-covered nanoparticles with biferrocene-terminated
alkanethiol, 1-(9-thiononyl-1-one)-1, 1-biferrocene (BFcS).
All sizes of Aun-BFc undergo two-step
oxidation reactions in 0.1 mol dm-3
Bu4NClO4-CH2Cl2
and consecutive potential scans including the second oxidation
process lead to the formation of an adhesive redox-active gold
nanoparticle film on an electrode. The thickness of the
Aun-BFc film is controllable by the
number of potential scans. The scanning tunneling microscope
images reveal that the Aun-BFc (d = 2.9 nm) film forms many domains of
the assembled Aun-BFcs, especially the
particles are isotropically assembled in line. 相似文献
13.
V. S. Kulikova A. F. Shestakov 《Russian Journal of Physical Chemistry B, Focus on Physics》2007,1(5):507-511
It was revealed that gold nanoparticles stabilized by a 1-dodecanethiol monolayer oxidize methane in a methylene chloride medium, presumably by the active oxygen species formed at the surface of the nanoparticles during their synthesis, to yield methanol (in stoichiometric amount), ethane, and an unidentified product. The same nanoparticles in a cyclohexene solution catalyze its oxidation by molecular oxygen to produce oxide (11%), alkylhydroperoxide (84%), and allyl ketone (5%). The only product of methane functionalization in toluene is ethylene. The results obtained on the oxidation of hydrocarbons suggest that, in the presence of gold nanoparticles, oxygen forms various active surface species, the structure of which is discussed. It is also demonstrated that gold nanoparticles catalyze multiple H-D exchange of methane with D2 (but not D+), an observation indicative of the activation of C-H bonds by a gold compound in the low oxidation state (Au0 or Au+). 相似文献
14.
A systematic study of the X2Aun (X = La, Y, Sc; n = 1–9) clusters are performed by using the density functional theory at TPSS level. The structures, stabilities, electronic, and magnetic properties are investigated in comparison with pure gold clusters. The results show that the transition points of the doped clusters from two-dimensional to three-dimensional structure are obviously earlier than gold clusters. The impurity X atoms tend to occupy the most highly coordinated position and form the largest probable number of bonds with gold atoms. In addition, the impurity atoms can strongly enhance the stabilities of gold clusters. It indicates that the impurity atoms dramatically affect the geometries and stabilities of the Aun clusters. The highest occupied molecular orbital–lowest occupied molecular orbital gap, vertical ionisation potential, and chemical hardness show that the X2Au6 clusters have higher stabilities than the others. In La2Au1–9, Y2Au1–7, and Sc2Au1–4 clusters, the charges transfer from X atoms to the Aun frames. The total magnetic moments of X2Aun clusters exist distinctly odd–even alternation behaviours except for La2Au4 and Sc2Au4 clusters. 相似文献
15.
V. G. Grigoryan D. Alamanova M. Springborg 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2005,34(1-3):187-190
The most stable structures of CuN, NiN, and AuN clusters with
2≤N≤60 have been determined using a combination of the
embedded-atom (EAM), the quasi-Newton, and our own
Aufbau/Abbau methods for the calculation of the total energy for a given structure, the structures of the local total-energy minima, and the structure of the global
total-energy minimum, respectively. We have employed two well-known versions of
the EAM: (1) the ‘bulk’ version of Daw, Baskes, and Foiles and (2) the Voter-Chen version which takes into account also properties of the dimer in the parameterization. The lower-energy structures (also for the smallest) of CuN and NiN clusters (i.e., structural details as well as symmetry)
obtained with the two versions are very similar. Thus, our study supports an universality of the bulk embedding functions for copper and nickel. But for gold clusters the differences
between structures calculated with the two different versions of the EAM are significant,
even for larger clusters. 相似文献
16.
X. J. Kuang X. Q. Wang G. B. Liu 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2011,61(1):71-80
An all-electron scalar relativistic calculation on
Au
n
NO (n = 1–10) clusters has been performed by using density functional
theory with the generalized gradient approximation at the PW91 level. The
small gold cluster would like to bond with nitric and the nitric monoxide
molecule prefers to occupy the on-top and single fold coordination site. The
Au
n
structures in all Au
n
NO clusters are only distorted slightly
and still keep the planar structures. With the bend of Au-N-O bond, the
structures of Au
n
NO clusters evolve from the 2D structure to 3D
structure. The most favorable adsorption between small gold cluster and
nitric monoxide molecule takes place in the case that nitric monoxide
molecule is adsorbed onto an odd-numbered pure Au
n
cluster and becomes
odd-numbered Au
n
NO cluster with even number of valence electrons. The
scalar relativistic effect strengthens the Au–Au, Au–N interaction and
weakens the N–O interaction, appearing as the shorter Au–Au, Au–N
bond-length and the longer N–O bond-length. The differences between our work
and previous work are believed to be the reflection of the scalar
relativistic effect. 相似文献
17.
Takeshi Eitoku Kazuya Taniguchi Yuta Nakazato Shunichi Ono Kenji Katayama 《Optical Review》2010,17(1):5-9
Formation process of gold nanoparticles was investigated by near-field heterodyne transient grating method. In the absence
of the protective agents, although the diffusion of H[AuICl2] could be observed after the photo-reduction of H[AuIIICl4], the diffusion of nanoparticle-seeds was not observed. On the other hand, in the presence of the protective agents, the
diffusion of a complex molecule (Au and protective agent) and nanoparticle-seeds could be observed. From these results, it
was found that enough amount of the complex is essential for the nanoparticle formation. We also investigated the formation
process with four different chemicals as a protective agent. The hydrodynamic radius of nanoparticle-seeds generated in the
poly(vinyl pyrrolidone) and TritonX-100 solutions were larger than those generated in the Tween 20 and Brij 58 solutions.
The former two have hydrophilic chain in the molecular structure; on the other hand, the latter two have hydrophobic alkyl
chain. Based on those facts, we concluded that the interaction between the chains of the complex molecule plays an important
role in the nanoparticle formation process. 相似文献
18.
The geometrical structures, relative stabilities, electronic and magnetic properties of calcium-doped gold clusters Au n Ca (n?=?1–8) have been systematically investigated by employing density functional method at the BP86 level. The optimised geometries show that the ground-state structures are planar structures for Au n Ca (n?=?3–8) clusters. Ca-substituted Au n +1 clusters, as well as Au-capped Au n ?1Ca clusters, are dominant growth patterns for the Au n Ca clusters. The relative stabilities of Au n Ca clusters for the ground-state structures are analysed based on the averaged binding energies, fragmentation energies and second-order difference of energies. The calculated results reveal that the Au2Ca isomer is the most stable structure for small size Au n Ca (n?=?1–8) clusters. The HOMO-LUMO energy gaps as a function of the cluster size exhibit a pronounced even–odd alternation phenomenon. Subsequently, charge transfers and magnetic moment of Au n Ca (n?=?1–8) clusters have been analysed further. 相似文献
19.
Monodisperse silica nanoparticles were synthesised by the well-known Stober protocol, then dispersed in acetonitrile (ACN)
and subsequently added to a bisacetonitrile gold(I) coordination complex ([Au(MeCN)2]+) in ACN. The silica hydroxyl groups were deprotonated in the presence of ACN, generating a formal negative charge on the
siloxy groups. This allowed the [Au(MeCN)2]+ complex to undergo ligand exchange with the silica nanoparticles and form a surface coordination complex with reduction to
metallic gold (Au0) proceeding by an inner sphere mechanism. The residual [Au(MeCN)2]+ complex was allowed to react with water, disproportionating into Au0 and Au(III), respectively, with the Au0 adding to the reduced gold already bound on the silica surface. The so-formed metallic gold seed surface was found to be
suitable for the conventional reduction of Au(III) to Au0 by ascorbic acid (ASC). This process generated a thin and uniform gold coating on the silica nanoparticles. The silica NPs
batches synthesised were in a size range from 45 to 460 nm. Of these silica NP batches, the size range from 400 to 480 nm
were used for the gold-coating experiments. 相似文献