共查询到20条相似文献,搜索用时 15 毫秒
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Wen-Kai Zhao Chuan-Lu YangJing-Fen Zhao Mei-Shan WangXiao-Guang Ma 《Physica B: Condensed Matter》2012,407(12):2247-2253
The transport properties of the cage-like molecule depend on its orientation between the electrodes, but the investigation on the mechanism has not been found. Using first-principle density-functional theory (DFT) and non-equilibrium Green’s function (NEGF) formalism for quantum transport calculation, we study the electronic transport properties of C24 fullerene molecule with different orientations in Au–C24–Au two-probe system. The effects of k-point sampling on the Brillouin zone are explored. Our results show that the negative differential resistance of C24 molecule is found in such a system and can be tuned by the molecule's orientation in the two-probe system. We also proposed a mechanism for it. The I–V characteristic under bias voltage is determined. The present findings could be helpful for the application of the C24 molecule in the field of single molecular devices or nanometer electronics. 相似文献
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Density functional theory has been employed to optimize the structure of endohedral doped C20 fullerene. We have also investigated electronic properties. We have found that C20 cage can accommodate up to 8 hydrogen atoms. Some hydrogen atoms get chemisorbed on the inner surface of C20 cage and form C-H bond. Structural deformation is found to increase with increase in H-atoms. From the analysis of electronic properties, we observe that due to endohedral doping of hydrogen atoms inside C20, H-atoms acquire net negative charge by accepting electrons and fullerene molecules acquire positive charge by donating electrons to H-atoms. For endohedral complexes where H3 triangular molecule formation takes place, the nature of net charge transfer changes, i.e. fractional electronic charge is transferred from H-atoms to fullerene. C20 doped with odd number of H-atoms should be more reactive compared to the even number case. Most of the present results are similar to those of endohedral C60. 相似文献
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Guomin JiDongmei Li Changfeng FangYuqing Xu Yaxin ZhaiBin Cui Desheng Liu 《Physics letters. A》2012,376(5):773-778
Using first-principles calculations, we study the electronic transport properties in Au(C20)2Au molecular junctions with different contact interface configurations: point contact and bond contact. We observe that the transmission through the bond contact is considerably higher than that of point contact. Furthermore, the I-V characteristics are rather different. For the bond contact, we get a metallic behavior followed by a varistor-type behavior. While as for the point contact, the current increases very slowly in a nonlinear way and is one order of magnitude smaller than that of bond contact. We attribute these obvious differences to the distinct contact configurations. 相似文献
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Using an ab initio method based on non-equilibrium Green’s functions (NEGF) combined with density functional theory (DFT), a calculation of the transport properties of a single molecular junction based on 1,3-diphenylpropynylidene (PhC3Ph) ‘radical-π-radical’ is performed. The obvious negative differential resistance (NDR), spin current polarisation (SCP) and dual-spin current rectification (SCR) effects in this device are obtained. The total current for magnetic parallel configuration (PC) is larger at first and then less than that for magnetic antiparallel configuration (APC) as the bias increases, which suggests the abnormal magnetoresistance (MR) effect and can be used as a molecular switch with two working voltages. The evolution of the spin-polarised transmission spectrums and the frontier molecular orbitals (MOs) with applied bias is used to explain the above interesting results. Our calculations may be helpful for designing multifunctional molecular spintronics devices in the future. 相似文献
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Hydration effect on the electronic transport properties of oligomeric phenylene ethynylene molecular junctions 下载免费PDF全文
A first-principles computational method based on the
hybrid density functional theory is developed to simulate the
electronic transport properties of oligomeric phenylene ethynylene
molecular junctions with H2O molecules accumulated in the
vicinity as recently reported by Na {\it et al.}
[\wx{Nanotechnology}{18} 424001 (2007)]. The numerical results show
that the hydrogen bonds between the oxygen atoms of the oligomeric
phenylene ethynylene molecule and H2O molecules result in the
localisation of the molecular orbitals and lead to the lower
transition peaks. The H2O molecular chains accumulated in the
vicinity of the molecular junction can not only change the
electronic structure of the molecular junctions, but also open
additional electronic transport pathways. The obvious influence of
H2O molecules on the electronic structure of the molecular
junction and its electronic transport properties is thus
demonstrated. 相似文献
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Yi-Peng An Chuan-Lu Yang Mei-Shan Wang Xiao-Guang Ma De-Hua Wang 《Current Applied Physics》2010,10(1):260-265
The transport properties of the endohedral Li@C20 metallofullerene are studied using density functional non-equilibrium Green’s function method. The equilibrium conductance of Li@C20 metallofullerene becomes larger than that of the empty C20 fullerene molecule. The I–V curve under low-bias voltage shows the characteristic of metallic behavior; another, the novel negative differential resistance behavior is also observed. It is found that the doping effect of Li atom significantly changes the transport properties of C20 fullerene. 相似文献
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We apply the nonequilibrium Green's function method based on density functional theory to investigate the electronic and transport properties of waved zigzag and armchair graphene nanoribbons. Our calculations show that out-of-plane mechanical deformations have a strong influence on the band structures and transport characteristics of graphene nanoribbons. The computed I-V curves demonstrate that the electrical conductance of graphene nanoribbons is significantly affected by deformations. The relationship between the conductance and the compression ratio is found to be sensitive to the type of the nanoribbon. The results of our study indicate the possibility of mechanical control of the electronic and transport properties of graphene nanoribbons. 相似文献
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采用密度泛函理论中的广义梯度近似对Ni@C20H20的几何结构、成键和电磁性质进行密度泛函计算研究.结构优化发现位于偏离笼子中心三种位置处的Ni原子优化之后均回到笼子中心.结合能和能隙分析表明C20H20的中心位置是Ni原子热力学和动力学最稳定的位置.成键分析表明:Ni原子位于C20H20中心时,和C原子之间几乎没有相互作用,保持自己的孤立状态.电磁分析表明:原子磁矩为2关键词:
20H20')" href="#">C20H20
20H20')" href="#">Ni@C20H20
几何结构
成键
电磁性质
密度泛函理论 相似文献
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Robert Hellmann 《Molecular physics》2013,111(3):387-401
A four-dimensional potential energy hypersurface (PES) for the interaction of two rigid nitrogen molecules was determined from high-level quantum-chemical ab initio computations. A total of 408 points for 26 distinct angular configurations were calculated utilizing the counterpoise-corrected supermolecular approach at the CCSD(T) level of theory and basis sets up to aug-cc-pV5Z supplemented with bond functions. The calculated interaction energies were extrapolated to the complete basis set limit and complemented by corrections for core–core and core–valence correlations, relativistic effects and higher coupled-cluster levels up to CCSDT(Q). An analytical site–site potential function with five sites per nitrogen molecule was fitted to the interaction energies. The PES was validated by computing second and third pressure virial coefficients as well as shear viscosity and thermal conductivity in the dilute-gas limit. An improved PES was obtained by scaling the CCSDT(Q) corrections for all 408 points by a constant factor, leading to quantitative agreement with the most accurate experimental values of the second virial coefficient over a wide temperature range. The comparison with the best experimental data for shear viscosity shows that the values computed with the improved PES are too low by about 0.3% between 300 and 700?K. For thermal conductivity large systematic deviations are found above 500?K between the calculated values and most of the experimental data. 相似文献
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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
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Ab initio calculation of electronic transition moments for singlet excited states of the H2 molecule
Annie Spielfiedel 《Journal of Molecular Spectroscopy》2003,217(2):162-172
Ab initio CI electronic dipole transition moments have been calculated for the transitions between singlet states of the hydrogen molecule correlating asymptotically with H(nl)+H(1s) (n=1,2,3). The investigated singlet-singlet transitions include the 30 (n=3) inter-Rydberg transitions and the 32 transitions which may contribute to absorption in the far wings of the Balmer α line of atomic hydrogen perturbed by another hydrogen atom in its ground state. Results are presented for internuclear distances 1.0a0?R?12a0. The present results compare well with the previous theoretical calculations available for about half of the transitions treated in the present work. Thirty eight new transitions are presented. Adiabatic potential energies for the and and improved energies for the and states are reported as well. 相似文献
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Suleyman Cabuk 《哲学杂志》2016,96(2):190-207
The linear and non-linear optical properties of BiAlO3 are studied by employing the density functional perturbation theory within the local density and generalized gradient approximations. The computations are based on the electronic structure obtained within density functional theory. The optical properties such as the dielectric function, refractive index, spectral reflectivity, absorption coefficient and electron energy-loss spectrum are obtained in the energy region of up to 30 eV. The calculated value of the birefringence for BiAlO3 shows that it is a uniaxial negative crystal and has a large birefringence. We also report our studies on the second harmonic generation response coefficient over a large frequency range for BiAlO3 crystal. The predicted second-order optical spectra indicate pronounced structures related to of 1ω and 2ω frequency resonances. Furthermore, the non-linear optic and linear electro-optic coefficients are computed by employing 2n + 1 theorem applied to an electric-field dependent energy functional. The results are compared with the available calculations. 相似文献
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Tao Wang 《Applied Surface Science》2006,252(14):4943-4950
A theoretical comparison of C54 and C49 TiSi2 surfaces is presented, using ab initio plane-wave ultrasoft pseudopotential method based on generalized gradient approximation (GGA). The different surface energies of TiSi2 have not only been calculated out, but the preferential formation of C49 phase in solid-state reaction could be explained by smaller surface energies and Poisson's ratio of C49 TiSi2 as well. As for polar C54 TiSi2(1 0 0) and C49 TiSi2(0 1 0) surfaces, the Si termination surfaces are more stable. 相似文献
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The intermolecular potential energy surface for C3–He complex has been constructed using supermolecular CCSD(T) and MP4 methods. The potential surfaces have been calculated for 27 values of R ranging from 2.8 to 8.0 Å and 19 values of θ equally spaced between 0° and 180°. Both CCSD(T) and MP4 potentials have similar global behaviors. The global minimum in each of the potentials corresponds to the slightly distorted T-shaped geometry. On the basis of these two potentials, the intermolecular vibrational energies and wavefunctions were calculated. The energy level pattern of the vdW vibrational states was predicted for C3–He complex. The zero point bending motion of this complex has a range of 180°. The calculated fundamental frequency of vdW bending is 3.16 cm?1 at CCSD(T) level, and 5.38 cm?1 at the MP4 level. In addition, we have also constructed the intermolecular potential energy surface with C3 bending coordinate of 160° by using supermolecular CCSD(T) method. Two local minima including arrow-shaped and Y-shaped configurations were determined. The rotational constants of three C3–He structures including T-shaped, arrow-shaped and Y-shaped configurations at CCSD(T) level were also reported. 相似文献
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Zhi Liang 《Molecular physics》2013,111(10):1285-1295
The density, isochoric heat capacity, shear viscosity and thermal conductivity of CO2 gas in the pressure range of 1–50 atm and 300 K are calculated based on a five-centre potential model obtained from ab initio calculations of the intermolecular potential of a CO2 dimer. The quantum effects of the intramolecular motion are included in a model by the Monte Carlo (MC) Method. Without using any experimental data, the present model achieves excellent agreements between the calculated thermophysical properties and experimental data for all simulated CO2 densities except the highest one at 135 kg/m3 (3 mol/L). The contributions of potential to the thermophysical properties of the moderate dense CO2 gas and their dependence on density are investigated in detail. 相似文献