共查询到20条相似文献，搜索用时 15 毫秒
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This paper systematically studies the rolling effects of the (n, n) single-wall carbon nanotubes (SWCNT) with different curvatures on Rh adsorption behaviours by using density functional theory. The outside charge densities of SWCNTs are found to be higher than those inside, and the differences decrease with the increase of the tube radius. This electronic property led to the discovery that the outside adsorption energies are higher than the inside ones, and that the differences are reduced with the increase of the tube radius. Partial density of states and charge density difference indicate that these strong interactions induce electron transfer between Rh atoms and SWCNTs. 相似文献
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利用基于密度泛函理论的计算方法,研究了处于石墨（HOPG）表面的半导体性单壁碳纳米管,发现碳纳米管下面的石墨受碳管的作用向下凹陷,而纳米管本身虽然保持其形状不变,但它的电子态受石墨衬底影响,造成导带下移,禁带宽度明显减小.关键词：单壁碳纳米管密度泛函理论局域密度近似方法 相似文献
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碳纳米管中α-Ga和β-Ga纳米线相对稳定性的理论研究 总被引：1，自引：0，他引：1
采用密度泛函理论研究了碳纳米管中填充的金属镓纳米线的稳定性.结果表明,无论是在碳纳米管内的受限空间,还是在自由空间,较大尺寸的β-Ga纳米线都要比α-Ga纳米线稳定.通过对镓纳米线的平均能量和镓纳米线与碳纳米管间的结合能的分析,揭示了实验中观测到碳纳米管中金属镓会存在β-Ga相而无α-Ga相的物理原因.关键词：碳纳米管纳米线密度泛函理论 相似文献
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对闭口碳纳米管(CNT)顶端分层掺氮及吸附不同数目水分子体系,运用第一性原理研究了有电场存在时的电子场发射性能.结果表明：掺氮并吸附水分子的CNT结构稳定;外电场愈强、水分子数愈多,体系态密度(DOS)向低能端移动幅度愈大且最高分子占据轨道(HOMO)/最低分子空轨道(LUMO)能隙愈小.吸附能,DOS/LDOS,HOMO/LUMO及其能隙分析一致表明,第三层氮掺杂CNT吸附不同数目水分子体系的场发射性能最佳.关键词：氮掺杂水吸附密度泛函理论电子场发射 相似文献
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In this paper, we report that an electromotive force (EMF)can be induced in a rope of aligned single-walled carbon nanotubes(SWNTs) when water droplets fall on this rope. The magnitude of thisEMF depends sensitively on the slant angle of the SWNTs. Mostinterestingly, both the magnitude and the direction of the inducedEFM can be modulated by applying a current to the SWNTs. Theconcepts of electrical slip and no-slip are proposed and can bequantitatively described by ``electrical slip resistance'. Thiskind of generator does not need any magnet, rotor, {etc} and showsquite a different operating mechanism and design compared with aconventional large scale hydroelectric power generator. 相似文献
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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
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Using density functional theory, we present a model to illustrate that under a transverse electric field the overall amount of hydrogen storage can be increased on the SiC nanotube. Due to the cylindrical shape of the nanotube, an electric field does not have the similar effects on the different adsorption sites. Although it has the desired effects on some sites, the electric field may lead the binding energy to decrease on some other sites. We demonstrate that the binding energy decreases slightly just on the two small areas and increases significantly on the largest part of the nanotube surface. 相似文献
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本文采用第一性原理的密度泛函理论,主要以(6,6)Armchair型,(11,0)Zigzag型单壁碳纳米管为研究对象,研究了水分子链在碳纳米管内部吸附的稳定结构,以及结合能随其结构的变化.结果表明:当水分子链受限于碳纳米管内部时,引起碳纳米管直径收缩,这主要是由于水分子链与碳纳米管之间的氢键作用以及范德华弱相互作用所引起的.随着碳纳米管半径的增加,两种单体之间的结合能逐渐减小,但当碳纳米管半径增加至6.78时,其结合能又有所增加,这是由于在优化过程中,水分子链单体之间的氢键作用大于水分子链与碳纳米管之关键词：水分子链/单壁碳纳米管密度泛函理论结构稳定性 相似文献
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利用密度泛函理论研究了Li原子修饰的C24团簇的储氢性能. Li原子在C24团簇表面的最佳结合位是五元环. Li原子与C24团簇之间的作用强于Li原子之间的相互作用, 能阻止它们在团簇表面发生聚集. 当Li原子结合到C24表面时, 它们向C原子转移电子后带正电荷. 当氢分子接近这些Li原子时, 在电场作用下发生极化, 通过静电相互作用吸附在Li原子周围. 在Li修饰的C24复合物中, 每个Li原子能吸附两到三个氢分子, 平均吸附能处于0.08到0.13 eV/H2范围内. C24Li6能吸附12个氢分子, 储氢密度达到6.8 wt%. 相似文献
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As a candidate for hydrogen storage medium, geometric stability and hydrogen capacity of Ca-decorated graphene with topological defects are investigated using the first-principle based on density functional theory (DFT), specifically for the experimentally realizable single carbon vacancy (SV), 585 double carbon vacancy (585 DCV) and 555–777 double carbon vacancy (555–777 DCV) defects. It is found that Ca atom can be stabilized on above defective graphenes since Ca׳s binding energy on vacancy defect is much larger than its cohesive energy. Up to six H2 molecules can stably bind to a Ca atom on defective graphene with the average adsorption energies of 0.17–0.39 eV/H2. The hybridization of the Ca-3d orbitals with H2-σorbitals and the electrostatic interaction between the Ca cation and the induced H2 dipole both contribute to the H2 molecules binding. Double-side Ca-decorated graphene with 585 DCV and 555–777 DCV defects can theoretically reach a gravimetric capacity of 5.2 wt% hydrogen, indicating that Ca-decorated defective graphene can be used as a promising material for high density hydrogen storage. 相似文献
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Qing-Xiao Zhou Chao-Yang Wang Zhi-Bing Fu Yong-Jian Tang Hong Zhang 《Frontiers of Physics》2014,9(2):200-209
The geometries,formationenergies and electronic band structures of （8, 0） and （14, 0） singlewailed carbon nanotubes （SWCNTs） with various defects, inehlding vaeaney, Stone-Wales defect, and octagon pentagon pair defect, have been investigated within the framework of the density- huictional theory （DFT）, and the influence of the concentration within the same style of deflect on the physical and chenfical properties of SWCNTs is also studied. The results suggest that the existeilcc of vacancy and octagon-pentagon pair deflect both reduce the band gap, whereas the SW- defect induces a band gap opening in CNTs. More int, erestingly, the band gaps of （8, 0） and （14, 0） SWCNTs eonfigurations with two octagon pentagon pair defect presents 0.517 eV and 0.163/eV, which arc a little smaller than the perfectt CNTs. Furthermore, with the concentration of defects increasing, there is a decreasing of band ga.p making the two types of SWCNTs change from a semiconductor to a metallic conductor. 相似文献
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The influencing range of a vacancy defect in a zigzagsingle-walled nanotube is characterized with both structuraldeformation and variation in bandstructure. This paper proposes amicroscopic explanation to relate the structural deformation to thebandstructure variation. With an increasing defect density, thenanotubes become oblate and the energy gap between the deeplocalized gap state and the conducting band minimum state decreases.Theoretical results shed some light on the local energy gapengineering via vacancy density for future potential applications. 相似文献
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The phonon dispersion relations of three kinds of 4~?carbon nanotubes are calculated by using the density functionalperturbation theory. It is found that the frequencies of some phononmodes are very sensitive to the smearing width used in thecalculations, and eventually become negative at low electronictemperature. Moreover, two kinds of soft modes are identified forthe (5,0) tube which are quite different from those reportedpreviously. Our results suggest that the (5,0) tube remains metallicat very low temperature, instead of the metallic-semiconductingtransition claimed before. 相似文献
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The phonon dispersion relations of three kinds of 4 carbon nanotubes are calculated by using the density functional perturbation theory. It is found that the frequencies of some phonon modes are very sensitive to the smearing width used in the calculations, and eventually become negative at low electronic temperature. Moreover, two kinds of soft modes are identified for the (5,0) tube which are quite different from those reported previously. Our results suggest that the (5,0) tube remains metallic at very low temperature, instead of the metallic-semiconducting transition claimed before. 相似文献
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This paper studies the quantum conductance properties ofthree-terminated carbon nanotube Y-junctions, which are built byconnecting three (5,5) single-walled carbon nanotubes. The resultsshow that the quantum conductance at the Fermi energy oscillatesperiodically with the junction's size, and the number of oscillatingperiodic layers is 3 which is the same as that in the two terminated$(10,0)/m(5,5)/(10,0)$ junctions. Moreover, this Y-junction withdifferent size exhibits obvious different distribution of electroncurrent in the two drain branches, called shunt valve effect ofelectronic current. Thus the degree of this effect can be controlledand modulated directly by constructing the three branches' sizes orthe distribution of defect. The results show in detail that thedifference between the two drain currents can be up to two times forsome constructions with special sizes. In addition, the uniformdistribution of defects in the Y-junction leads to lower quantumconductance than that of other defect configurations. 相似文献