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1.
We have studied the switching characteristics of an optical molecular switch based on the 15,16-dinitrile dihydropyrene/cyclophanediene (DDP/CPD) molecule with two single-walled carbon nanotube (SWCNT) electrodes using first-principles transport calculations. It is shown that the DDP shows an overall higher conductance than the CPD at low bias which is independently of the SWCNT chirality. Meantime, the conductance of the molecular switch can be tuned by the chirality of the SWCNT.  相似文献   

2.
Applying nonequilibrium Green's function formalism in combination with the first-principles density functional theory, we investigate the electronic transport properties of optical molecular switch based on the fulgide molecule with two different single-walled carbon nanotube (SWCNT) electrodes. The molecule that comprises the switch can convert between E isomer and C isomer by ultraviolet or visible irradiation. Theoretical results show that these two isomers exhibit very different conductance properties both in armchair and zigzag junction, which can realize the on and off states of the molecular switch. Meantime, the chirality of the SWCNT electrodes strongly affects the switching characteristics of the molecular junctions, which is useful for the design of functional molecular devices.  相似文献   

3.
Based on the nonequilibrium Green function method and density functional theory calculations,we theoretically investigate the effect of chirality on the electronic transport properties of thioxanthene-based molecular switch.The molecule comprises the switch which can exhibit different chiralities,that is,cis-form and trans-form by ultraviolet or visible irradiation.The results clearly reveal that the switching behaviors can be realized when the molecule converts between cis-form and trans-form.Furthermore,the on-off ratio can be modulated by the chirality of the carbon nanotube electrodes.The maximum on-off ratio can reach 109 at 0.4 V for the armchair junction,suggesting potential applications of this type of junctions in future design of functional molecular devices.  相似文献   

4.
Using nonequilibrium Green's function formalism combined first-principles density functional theory, we analyze the transport properties of a 4,4-dimethyl-6-(4-nitrophenyl)-2-phenyl-3,5-diaza-bicyclo[3.1.0]hex-2-ene molecular optical switch. The title molecule can convert between closed and open forms by visible or ultraviolet irradiation. The I-V characteristics, differential conductance, on-off ratio, electronic transmission coefficients, spatial distribution of molecular projected self-consistent Hamiltonian orbitals, HOMO-LUMO gaps, effect of electrode materials Y(111)(Y =Au, Ag and Pt) on electronic transport and different molecular geometries corresponding to the closed and open forms through the molecular device are discussed in detail. Based on the results, as soon as possible the open form translates to the closed form, and there is a switch from the ON state to the OFF state(low resistance switches to high resistance). Theoretical results show that the donor/acceptor substituent plays an important role in the electronic transport of molecular devices. The switching performance can be improved to some extent through suitable donor and acceptor substituents.  相似文献   

5.
The influence of structure on the thermal conductivities of single-wall carbon nanotubes (SWCNTs) and graphene nanoribbons (GNRs), is investigated by using molecular dynamics (MD) method. The calculated results demonstrate that, both edge/chirality and width/diameter affect the thermal conductivities of these two low-dimensional carbon materials in nanoscale. However, the effects of structure on the thermal conductivities of SWCNTs and GNRs are different from each other. It is concluded that the influence of structure on the thermal conductivities of SWCNTs and GNRs is not stronger than that on their electric conductivities.  相似文献   

6.
The effects of nickel coating on the torsional behaviors of single-walled carbon nanotubes (SWCNTs) subject to torsion motion are investigated using the molecular dynamics (MD) simulation method. The simulation results show that regardless of chirality, defect or radius, nickel coating can considerably enhance the critical torque of SWCNTs. However, by comparing the critical torsion angle between nickel-coated SWCNTs and corresponding pristine SWCNTs, it is found that nickel coating in small-radius nanotubes does induce a reduction in the critical torsion angle. The results also show that the structural failure of nickel coated imperfect (9,0) SWCNT occurs at an obviously higher critical torque in comparison with uncoated (9,0) SWCNT with a vacancy defect. Furthermore, we also find that the critical torque of a short nickel coated SWCNT is bigger than that of a long one, while the critical torsion angle for a short tube is smaller than that for a long one.  相似文献   

7.
使用分子动力学方法模拟了单壁碳纳米管的拉伸变形行为和泊松比,并从单壁碳纳米管晶胞单元的结构特征角度,系统分析了管径、螺旋性和应变对力学性能的影响.模拟结果显示,单臂性碳纳米管(8,8)-(22,22)和锯齿性碳纳米管(9,0)-(29,0)的拉伸弹性变形可以分别达到35%-38%和20%-27%,拉伸条件下这些碳纳米管的弹性模量随管径的增大从960 GPa下降到750 GPa,并且锯齿性碳纳米管的弹性模量比单臂性碳纳米管的弹性模量要高.通过对三根具有相同直径和不同螺旋性的碳纳米管(9,9),(12,6)和(16,0)分别在拉伸和压缩条件下的模拟发现,随着变形的增大,碳纳米管的泊松比将减小;在相同的拉伸应变下,碳纳米管的泊松比随其螺旋角的减小而减小,而在相同的压缩应变下,碳纳米管的泊松比随其螺旋角的减小而增大.  相似文献   

8.
采用巨正则蒙特卡罗方法(GCMC)研究了单壁氮化硼纳米管(SWBNNTs)和单壁碳纳米管(SWCNTs)的物理吸附储氢性能,主要对比研究了纳米管的管径、温度和手性对二者物理吸附储氢量的影响. 研究结果表明:在低温下,SWBNNTs的物理吸附储氢性能优于相应的SWCNTs;但是随着温度的升高,二者的物理吸附储氢性能差别越来越小,在常温下,SWBNNTs不具备有比SWCNTs更强的物理吸附储氢性能,而是和相同条件下的SWCNTs相差不大,只是在高压下的物理吸附储氢量稍稍大于SWCNTs,并给出了合理的理论解释 关键词: 巨正则蒙特卡罗方法(GCMC) 单壁氮化硼纳米管(SWBNNTs) 单壁碳纳米管(SWCNTs) 储氢  相似文献   

9.
Eringen's nonlocality is incorporated into the shell theory to include the small-scale effects on the axial buckling of single-walled carbon nanotubes (SWCNTs) with arbitrary boundary conditions. To this end, the Rayleigh-Ritz solution technique is implemented in conjunction with the set of beam functions as modal displacement functions. Then, molecular dynamics simulations are employed to obtain the critical buckling loads of armchair and zigzag SWCNTs, the results of which are matched with those of nonlocal shell model to extract the appropriate values of nonlocal parameter. It is found that in contrast to the chirality, boundary conditions have a considerable influence on the proper values of nonlocal parameter.  相似文献   

10.
We develop a robust theoretical method for the determination of local chirality based on individual hexagons that compose single-walled carbon nanotubes (SWCNTs). The method and code are applied to various SWCNT-like irregular structures that are formed during the growth process. The local chiral index and its distribution are well defined for irregular structures as well as ideal structures of SWCNTs, and can be used to characterize any SWCNT-like irregular structures in terms of local chirality. The present method also permits monitoring the chirality of nanostructures during the growth process.  相似文献   

11.
In this article, mechanical properties of single-walled carbon nanotubes (SWCNTs) with various radiuses under tensile, compressive and lateral loads are considered. Stress–strain curve, elastic modulus, tensile, compressive and rotational stiffness, buckling behaviour, and critical axial compressive load and pressure of eight different zigzag and armchair SWCNTs are investigated to figure out the effect of radius and chirality on mechanical properties of nanotubes. Using molecular dynamic simulation (MDS) method, it can be explained that SWCNTs have higher Young’s modulus and tensile stiffness than compressive elastic modulus and compressive stiffness. Critical axial force of zigzag SWCNT is independent from the radius, but that of armchair type rises by increasing of radius, also these two types show different buckling modes.  相似文献   

12.
We investigate the influence of edge chirality on the electronic transport in clean or disordered graphene ribbon junctions. By using the tight-binding model and the Landauer-Büttiker formalism, the junction conductance is obtained. In the clean sample, the zero-magnetic-field junction conductance is strongly chirality-dependent in both unipolar and bipolar ribbons, whereas the high-magnetic-field conductance is either chirality-independent in the unipolar or chirality-dependent in the bipolar ribbon. Furthermore, we study the disordered sample in the presence of magnetic field and find that the junction conductance is always chirality-insensitive for both unipolar and bipolar ribbons with adequate disorders. In addition, the disorder-induced conductance plateaus can exist in all chiral bipolar ribbons provided the disorder strength is moderate. These results suggest that we can neglect the effect of edge chirality in fabricating electronic devices based on the magnetotransport in a disordered graphene ribbon.  相似文献   

13.
Cai-Juan Xia  De-Sheng Liu  Han-Chen Liu 《Optik》2012,123(14):1307-1310
By applying nonequilibrium Green's function formalism combined first-principles density functional theory, we investigate the electronic transport properties of the phenylazoimidazole optical molecular switch. The molecule that comprises the switch can convert between the cis and the trans forms upon photoexcitation. The influence of HOMO–LUMO gaps and the spatial distributions of molecular orbitals on the electronic transport through the molecular device are discussed in detail. Theoretical results show that the current through the trans form is significantly larger than through the cis form, which suggests this system has attractive potential application in future molecular switch technology.  相似文献   

14.
The adsorption of glucose molecule on single-walled carbon nanotubes(SWCNTs)is investigated by density functional theory calculations.Adsorption energies and equilibrium distances are evaluated,and glucose binding to the typical semiconducting and metallic nanotubes with various diameters and chirality are compared.We also investigated the role of the structural defects on the adsorption capability of the SWCNTs.We could observe larger adsorption energies for the larger diameters semiconducting CNTs,while the story is paradoxical for the metallic CNTs.The obtained results reveal that the adsorption energy is significantly higher for nanotubes with higher chiral angles.Finally,the adsorption energies are calculated for defected nanotubes for various configurations such as glucose molecule approaching to the pentagon,hexagon,and heptagon sites in the tube surface.We find that the respected defects have a minor contribution to the adsorption mechanism of the glucose on SWNTs.The calculation of electron transfers and the density of states supports that the electronic properties of SWCNTs do not change significantly after the gluycose molecular adsorption.Consequently,one can predict that presence of glucose would neither modify the electronic structure of the SWCNTs nor direct to a change in the conductivity of the intrinsic nanotubes.  相似文献   

15.
By employing molecular mechanics and molecular dynamics simulations, we investigate the radial collapses and elasticities of different chiral single-walled carbon nanotubes(SWCNTs) with divacancy, and 5-8-5 defects. It is found that divacancy and 5-8-5 defect can reduce the collapse pressure(Pc) of SWCNT(10, 10) while 5-8-5 defect can greatly increase Pc of SWCNT(17, 0). For example, 5-8-5 defect can make Pc of SWCNT(17, 0) increase by 500%. A model is established to understand the effects of chirality, divacancy, and 5-8-5 defect on radial collapse of SWCNTs. The results are particularly of value for understanding the mechanical behavior of SWCNT with divacancy, and the 5-8-5 defect that may be considered as a filler of high loading composites.  相似文献   

16.
《Physics letters. A》2014,378(5-6):570-576
The elastic properties of single walled carbon nanotube (SWCNT) with surrounding water interactions are studied using molecular dynamics simulation technique. The compressive loading characteristic of carbon nanotubes (CNTs) in a fluidic medium such as water is critical for its role in determining the lifetime and stability of CNT based nano-fluidic devices. In this paper, we conducted a comprehensive analysis on the effect of geometry, chirality and density of encapsulated water on the elastic properties of SWCNT. Our studies show that defect density and distribution can strongly impact the compressive resistance of SWCNTs in water. Further studies were conducted on capped SWCNTs with varying densities of encapsulated water, which is necessary to understand the strength of CNT as a potential drug carrier. The results obtained from this paper will help determining the potential applications of CNTs in the field of nano-electromechanical systems (NEMS) such as nano-biological and nano-fluidic devices.  相似文献   

17.
The electronic transport properties of the salicylideneanilines-based molecular optical switch are investigated using a nonequilibrium Green's function formalism combined with first-principles density functional theory. The molecule that comprises the switch can convert between the enol and keto tautomeric forms upon photoinduced excited state hydrogen transfer in the molecular bridge. Theoretical results show that the current through the enol form is significantly larger than that through the keto form, which realize the on and off states of the molecular switch. The physical origin of the switching behaviour is interpreted based on the spatial distributions of molecular orbitals and the HOMO-LUMO gap. Furthermore the effect of the donor/acceptor substituent on the electronic transport through the molecular device is also discussed in detail. The switching performance can be improved to some extent through the acceptor substituent.  相似文献   

18.
The method using arc discharge in liquid is a simple and inexpensive route for synthesis of carbon nanotubes and other related nano-materials. In this study, we report the synthesis of single-wall carbon nanotubes (SWCNTs) by means of the arc-in-water method under extremely low gravity conditions. The strong heat convection caused by the arc plasma is suppressed under such conditions. Therefore, the boiling flow behavior and temperature distribution have been stabilized in low gravity. As a result, the possibility of the chirality control of SWCNTs by applying extremely low gravity was revealed; namely, the yield of semiconducting SWCNTs was increased and several SWCNTs of specific diameters turned out to be prominent under extremely low gravity conditions. PACS 52.80.Wq; 68.37.Lp; 81.07.De; 81.70.Ha; 82.80.Gk  相似文献   

19.
By applying non-equilibrium Green’s function (NEGF) formalism combined with first-principles density functional theory (DFT), we have investigated the electronic transport properties of the anthraquinone-based molecular switch. The molecule that comprises the switch can be converted between the hydroquinone (HQ) and anthraquinone (AQ) forms via redox reactions. The transmission spectra of these two forms are remarkably distinctive. Our results show that the current through the HQ form is significantly larger than that through the AQ form, which suggests that this system has attractive potential application in future molecular switch technology.  相似文献   

20.
Y.W. Li  J.H. Yao  J.W. Yang 《Physics letters. A》2009,373(43):3974-3977
The effect of O2 adsorption on the electron transport behavior of Fe-porphyrin molecule is investigated by the first-principles computational approach. The current-voltage characteristics of Fe-porphyrin and O2 adsorbed Fe-porphyrin between gold electrodes are calculated. We find that the conductance of the Fe-porphyrin decreases dramatically upon the adsorption of O2, which suggests that this system has potential application as a molecular sensor or a switch. This switching-behavior is analyzed from the evolutions of the transmission spectra and the molecular projected self-consistent Hamiltonian states of the molecular systems.  相似文献   

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