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1.
采用TLHT势和经典分子动力学方法研究了稀有气体原子(He,Ne,Ar,Kr,Xe)进入带缺陷的单壁纳米碳管(SWCNT)的动力学过程,计算出了稀有气体原子分别从管壁和管口入射时,它们能封装在SWCNT中的能量阈值Ek0,并与理想结构情形做了比较.结果表明:随着管壁缺陷半径r的增加,Ek0减小;当r<4.5 ?时,给定合适的初始动能,稀有气体原子能封装在纳米碳管中;而r=4.5 ?时,稀有气体原子不能封装在碳管中,且此时缺陷对Ar,Kr和Xe的输运特性有很大影响.
关键词:
纳米碳管
缺陷
稀有气体原子
分子动力学模拟 相似文献
2.
利用X射线衍射(XRD)和X射线吸收近边结构(XANES)方法研究了在Si(100)衬底上及600℃温度条件下用分子束外延(MBE)共蒸发方法生长的MnxSi1-x磁性薄膜的结构.由XRD结果表明,只有在高Mn含量(8%和17%)样品中存在着Mn4Si7化合物物相.而XANES结果则显示,对于Mn浓度在0.7%到17%之间的MnxSi1-x样品,其Mn原子的XANES谱表现出了一致的谱线特征.基于多重散射的XANES理论计算进一步表明,只有根据Mn4Si7模型计算出的理论XANES谱才能够很好的重构出MnxSi1-x样品的实验XANES谱.这些研究结果说明在MnxSi1-x样品中,Mn原子主要是以镶嵌式的Mn4Si7化合物纳米晶颗粒存在于Si薄膜介质中,几乎不存在间隙位和替代位的Mn原子.
关键词:
xSi1-x磁性薄膜')" href="#">MnxSi1-x磁性薄膜
分子束外延
XRD
XANES 相似文献
3.
采用密度泛函理论对H2与Rhn(n=1—8)团簇的相互作用进行了系统研究.结果表明, RhnH2体系的最低能量结构是在Rhn团簇最低能量结构的基础上吸附H原子生长而成.吸附H原子没有改变Rhn团簇的结构, 键长是影响Rhn和RhnH2磁矩的主要因素.从优化后的几何结构可以看出吸附后的H2发生断键,表明H2分子发生了解离性吸附.当n≤5,H原子的吸附以桥位为主,当n≥6时,H原子开始出现空位吸附.H原子的吸附提高了Rhn的稳定性和化学活性,较小的吸附能表明H原子易从RhnH2中解离出来.二阶能量差分表明4是RhnH2和Rhn团簇的幻数.
关键词:
nH2和Rhn团簇')" href="#">RhnH2和Rhn团簇
平衡结构
电子性质 相似文献
4.
采用基于密度泛函理论(DFT)中的广义梯度近似 (GGA),在考虑自旋多重度的情况下,对NiMgn(n=1—12)团簇进行了构型优化,频率分析和电子性质计算.结果表明:n=1,2时,体系的基态为自旋三重态,n≥3时,为单重态;Ni原子掺杂使主团簇结构发生了明显变化. n≤8时,三角双锥,四角双锥结构主导着NiMgn基态团簇的生长行为; n在9—12之间时,主团簇Mgn+1(n=1—12)的基于三棱柱构型的基态演化行为发生了一定程度的改变;n≥6时,Ni原子陷入了主团簇内部;掺杂使体系的平均结合能增大,能隙减小;n=4,6,10是团簇的幻数;不同尺寸团簇的s, p, d轨道杂化中,Ni原子3d, 4p成分所起作用不同; NiMg6基态结构具有很高的对称性(Oh),很好的稳定性和化学活性,能隙仅为0.25eV.
关键词:
n团簇')" href="#">NiMgn团簇
几何结构
稳定性
化学活性 相似文献
5.
通过采用密度泛函理论对Sc2,Y2和La2基本性质的计算,选择在较优理论水平下系统地研究了Scn, Yn和Lan(n=2—10)团簇的几何结构、稳定性、电子性质和磁性及其随团簇尺寸的变化趋势.此同族三种团簇的稳定性由原子密堆集几何结构效应决定,幻数均表现出一致的结果.Lan团簇的能隙比
关键词:
n')" href="#">Scn
n和Lan团簇')" href="#">Yn和Lan团簇
密度泛函理论
电子性质
磁矩 相似文献
6.
利用密度泛函理论(DFT)的B3PW91方法,在6-311G水平上对BMgn,AlMgn(n=1—12)团簇进行了几何结构优化和电子性质分析. 发现随着原子个数的增加, B原子进入镁团簇的内部, 而AlMgn和镁团簇有相似的生长模式. B,Al原子的掺杂均能使镁团簇的平均结合能增大,稳定性增强, BMgn,AlMgn关键词:
密度泛函理论
最低能量结构
n和AlMgn团簇')" href="#">BMgn和AlMgn团簇
NBO电荷布居 相似文献
7.
采用描述原子间相互作用的Lennard-Jones势来描述C60分子间的相互作用,考虑了每个C60分子的一定位置取向,并采用最速下降法计算了IH,fcc,hcp,DH及SC五种典型结构满壳层(C60)N团簇(N<2000)的能量.结果显示:当尺寸较小(N<20)时,IH结构最稳定;当尺寸处于中等(50<N<300)时,HCP结构最稳定;当尺寸较大(300<N
关键词:
60团簇')" href="#">C60团簇
取向
最速下降法
结构演化 相似文献
8.
9.
采用Gaussian 98程序,运用B3LYP方法,对Pd和Pb原子采用收缩价基组LANL2DZ,对Pb2和PdPb2分子的微观结构进行了理论计算. 由于Pb2分子离解后一个Pb原子处于基态,另一个Pb原子处于激发态,采用最小二乘法拟合Pb2分子的势能函数,选用的函数形式为Murrell-Sorbie势能函数加上开关函数. 使用多体展式理论导出了势函数中的参数进而给出PdPb2分子基态势函数的解析表达式,其势能面准确地复现了PdPb2分子的两个稳定构型(C2V和C∞v)及其能量关系.
关键词:
2')" href="#">Pb2
2')" href="#">PdPb2
势能函数 相似文献
10.
构造了考虑吸附与偏析相互作用情况下无序二元合金RhxPt1-x(110)吸附氧表面的原子集团模型,其中O的覆盖度为0.5;构造了考虑杂质Ni,Cu,W对合金可能产生影响的吸附表面原子集团模型,杂质的掺入采用替位式.应用recursion方法计算了合金表面的环境敏感镶嵌能和电子结构.环境敏感镶嵌能计算表明杂质Ni,Cu和W均使O吸附RhxPt1-x(110)合金表面
关键词:
化学吸附
表面偏析
recursion方法
态密度 相似文献
11.
O. O. Adisa B. J. Cox J. M. Hill 《The European Physical Journal B - Condensed Matter and Complex Systems》2011,79(2):177-184
In this paper we investigate methane packing in single-walled carbon nanotubes. We employ classical applied mathematical modelling
using the basic principles of mechanics to exploit the Lennard-Jones potential function and the continuous approximation,
which assumes that intermolecular interactions can be approximated by average atomic surface densities. We consider both zigzag
and spiral configurations formed by packing methane molecules into (9, 5), (8, 8) and (10, 10) carbon nanotubes, and we derive
analytical expressions for the interaction potential energy of these configurations. Our findings indicate that for the zigzag
configuration for a (9, 5) tube, the potential energy of the system is minimized when the methane molecules simply form a
linear chain along the tube axis, but genuine zigzag patterns are found as the tube size increases such as for the (8, 8)
and (10, 10) tubes. For the spiral configuration, the potential energy of the system is minimized when the angular spacing
is approximately equal to π for the (9, 5) and (8, 8) tubes, and π/2 for the (10, 10) tube. Overall, our results are in good agreement with molecular dynamics simulations in the literature
and show that the most energetically efficient packing configuration of the three tubes studied, occurs for a (10, 10) tube
with a zigzag packing, while a (10, 10) tube with a spiral packing configuration has the largest free-cavity volume for methane
adsorption at higher temperatures. 相似文献
12.
利用巨正则系综蒙特卡罗(GCMC)的方法模拟了氢在多壁碳纳米管中的吸附,氢气分子之间、氢气分子和碳原子之间的相互作用势能采用Lennard-Jones势能模型。模拟了不同结构参数(管内径、管壁数、管壁间距)的多壁碳纳米管在77K和298K下的吸附等温线,分析了多壁碳纳米管的管内径、管壁数以及管壁间距对吸附性能的影响。模拟结果表明:多壁碳纳米管的管壁数和管壁间距对吸附性能的影响较明显;管壁数越少,管壁间距越大,其吸附性能越好;多壁碳纳米管的管内径对其吸附性能的影响甚微。 相似文献
13.
14.
The dissociation energy and equilibrium bond length as explicit parameters are used to establish an improved five-parameter exponential-type potential energy model for diatomic molecules. We demonstrate that the five-parameter exponential-type potential is identical to the Tietz potential for diatomic molecules. It is observed that the improved five-parameter exponential-type potential can well model the internuclear interaction potential energy curve for the ground electronic state of the carbon monoxide molecule by the utilization of the experimental values of three molecular constants. 相似文献
15.
The ejection of DNA molecules from carbon nanotubes is reported from interaction energy perspectives by molecular dynamics simulations. The critical ejection energy, which is to be applied to a DNA molecule for a successful ejection from a carbon nanotube, is investigated based on a study on the friction and binding energy between the DNA molecule and the tube. An effective ejection is realized by subjecting a kinetic energy on the DNA molecule that is larger than the solved critical ejection energy. In addition, the relationship between ejection energies and sizes of DNA molecules and carbon nanotubes is investigated. 相似文献
16.
碳纳米管管腔作为分子物质的纳米通道,其储存或输送水的能力具有重要研究价值.为了研究碳纳米管管腔受限空间对水分子团簇结构和分布的影响,本文采用分子动力学方法探究了管径、手性和温度对单壁碳纳米管管腔内水的结构和分布的影响.结果表明:在常温下,管径尺寸范围为1.018—1.253 nm的单壁碳纳米管管内易形成有序的多元环水结构,此范围以外碳纳米管管内难以形成水的有序结构;且随着管径尺寸增大,多元环水呈现由三元环至六元环的结构变化;范德瓦耳斯势分布分析表明,在上述管径范围内,水分子趋向于贴近碳纳米管管壁分布而形成水的有序结构.对比管径尺寸差别较小的碳纳米管,其手性对多元环水结构影响不大.多元环水结构的稳定性表现出温度依赖性,管径较大的碳纳米管内的多元环水的有序结构更易随温度升高而消失. 相似文献
17.
运用分子动力学方法模拟了锯齿型双壁碳纳米管体系的振荡行为,其中旋转的内管施加了不同大小的螺旋上升长度.不同于以前关于扶手椅型碳纳米管的工作(Zeng Y H,et al.2016 Nanotechnology 27 95705),锯齿型的内管在施加了不同大小的螺旋上升长度之后,其管壁结构会产生畸变或缺陷.模拟过程中,锯齿型内管在施加一定的旋转速度以后保持自由,而固定的外管为无任何缺陷的理想锯齿型碳纳米管.分子动力学模拟结果显示锯齿型内管的轴向振荡行为与内管施加的螺旋上升长度密切相关.内管的振荡频率随着内管螺旋上升长度的增加而增加.但当内管的螺旋上升长度较大时,由于螺旋上升所引起的内管缺陷结构造成整个内管的破裂,从而导致其无法进行稳定的轴向振荡.模拟结果还显示,对于无螺旋上升的理想锯齿型碳管,虽然其轴向振荡效果非常微弱,但却可以作为一种具有恒定旋转频率的旋转致动器.此外,对螺旋上升长度为0.5 nm的内管在不同温度下的振荡性能进行了模拟分析,结果表明内管振荡的幅度随温度的升高而相应地增加,但当温度超过一定的临界值后,内管不能保持稳定的振荡. 相似文献
18.
In this paper, the channeling behavior of deuterons in the energy of 1400 keV along the <100> channel of Si was studied by the simulation of the channeling Rutherford spectrum in the backscattering geometry. The simulation was done by taking three considerations into account: (i) a minimum random component of the beam which enters the sample because of the scattering ions from the surface, (ii) the dechanneling starts at the greater penetration depths and (iii) the dechanneling follows a Gompertz type sigmoidal function with the two parameters which present the dechanneling rate and range, respectively. The Levenberg–Marquardt algorithm was used to set the best characteristic channeling parameters, the penetration depth at which the dechanneling starts, the energy loss and the dechanneling rate and range. The energy dependence of the ratio of channeling to random energy loss of deuterons in the energy range 1–2 MeV is investigated by comparing the determined value with the ones obtained in the other references. 相似文献
19.
Shudong Wu 《Physica B: Condensed Matter》2011,406(24):4634-4638
The effects of transverse electric field on the energy levels of electron and heavy hole, exciton binding energy and excitonic absorption spectra of GaAs parabolic quantum wire are theoretically investigated in detail. The results indicate that the electron and hole energy levels, exciton binding energy, excitonic absorption coefficient and absorption energy becomes smaller with the increase of electric field. That is more significant at the condition of weaker parabolic confinement potential. The phenomena can be explained by the separation of overlap integral of the electron and hole at the ground states. 相似文献
20.
Thermal radiation and nonthermal radiation of the slowly changing dynamic Kerr--Newman black hole 下载免费PDF全文
Using the related formula of dynamic black hole, we have calculated the instantaneous radiation energy density of the slowly changing dynamic Kerr-Newman black hole. It is found that the instantaneous radiation energy density of a black hole is always proportional to the quartic of the temperature of the event horizon in the same direction. By using the Hamilton-Jacobin equation of scalar particles in the curved spacetime, the spontaneous radiation of the slowly changing dynamic Kerr-Newman black hole is studied. The energy condition for the occurrence of the spontaneous radiation is obtained. 相似文献