Dong Jin-Ming

Dependence of in-tube doping on the radius and helicity of single-wall carbon nanotubes

Using the Lennard-Jones interaction potential between the impurity atom and carbon atom, we have studied the dependence of in-tube impurity doping on the radius of a single-wall carbon nanotube (SWNT), as well as its helicity. The obtained results show that the radius of the most stably doped SWNT is different for different kinds of impurity atoms. This is useful for producing the required doped SWNT. In addition, it is found that the helicity of tube has a strong effect on the potential energy of the atoms doped in the SWNT.

Band structure of the non-oxide perovskite MgCNi3

Using the self-consistent full-potential linearized augmented plane wave method, we carry out the electronic structure calculations of MgCNi3 in the local spin density approximation (LSDA) of the density-functional theory. The LSDA solution is metal. The magnetic moment on the Ni ion is only 0.014 µB. There is a peak in the density of state just below the Fermi energy (Ef), which can be strongly correlated with various instabilities. After including the strong electron-electron correlation effects on the Ni 3d state by the on-site Coulomb interaction correction, the density of state is greatly redistributed, and the peak just below Ef disappears. The magnetic moment on the Ni ion becomes 0.66 µB. Both LSDA and LSDA+U have shown that the electronic states near the Fermi surface are dominated by the 3d orbital of Ni.

Dependence of in-tube carbon chain on the radius and helicity of single-wall carbon nanotubes

Using the Lennard-Jones interaction potential, we have studied the in-tube carbon-chain structure doped into single-wall carbon nanotubes (SWCNTs). Through minimizing the potential energy of the doped system, it is found that the optimal structure of the doping carbon chain is spiral, but not a straight line, when the radius of the SWCNT is larger than about 4.30A.

A Three-Josephson-Junction Device with Noise*

A Gaussian white noise model and a symmetric dichotomous noise model for a three-Josephson-junction device are studied. It is shown that the symmetric noise can produce net voltage (Its corresponding dc current is zero), which sterns from the multiplicative noise,the asymmetry of the potential or the asymmetry of the potential itselt; respectively for the Gaussian white noise model or for the dichotomous noise model. The net voltage is negative,and exhibits a peak with increasing the additive noise strength (the stochastic resonance). The dc current-voltage characteristics are calculated for the two models. In addition, we find that when the dc current is not zero, in some scope the absolute value of the dc voltage versus the additive noise strength also presents the stochastic resonance.

Infrared Absorption Spectra of Undoped and Doped Few-Layer Graphenes

The infrared absorption spectra of undoped few-layer graphenes with the layer number of N = 1–6, the hole- and electron-doped few-layer graphenes with the layer number of N = 1–4 have been studied based upon the tight-binding model. It is found that in contrast with the featureless optical spectrum of the undoped monolayer graphene, the undoped AB-stacking bi-, tri-, tetra- and more-layer graphene exhibit characteristic jumps in their infrared absorption (IR) spectra, which are caused by coupling between different layers. It is also found that the clear peaks exist in the IR spectra of the hole or electron-doped bi-, tri- and tetra-layer graphenes, which are induced by the strong IR transitions between their parallel valence or conduction bands. Based upon their different IR spectra, a powerful experimental tool has been proposed to identify accurately the layer number and doping type for the few-layer graphenes.

The Linear Optical Polarizability Spectra of Five C78 Isomers

Effects of anisotropy, symmetry, atom arrangement and Coulomb interaction on the linear optical polarizability spectra of five C78 isomers are theoretically studied by using the extended Su–Schrieffer–Heeger model with and without Coulomb interaction. The main results are as follows. 1) The spectra become anisotropic with respect to the direction of the electric field of light. The property is common in the niorlel with and without Coulomb interaction. 2) The symmetry and atom arrangement have grcat effects on the peak positions, strengths, and number. 3) The Coulomb interaction tends to shift peaks to higher energies and enhances the oscillator strengths at higher energies.

Heat Conductivity of One-Dimensional Carbon Chain in an External Potential

The heat transport in a one-dimensional (1D) carbon nanowire (CNW) lying in an external potential with different amplitudes and periods is studied by the non-equilibrium molecular dynamics method. It is found that the thermal conductivity of CNW is always anomalous, increasing with the CNW length and obeying the power law κ~N, in which α decreases with the increasing external potential amplitude. The thermal conductivity could be enhanced by the external potential with rather larger amplitudes, which means that an applied external potential could be an efficient tool to improve the heat conductivity of a real 1D material. In addition, the effect of different periods of the external potential is studied, finding the external potential with an incommensurate period leads to the smaller α value.

Charge-Orbital Ordering in Ferromagnetic and Charge-Exchange-Type Antiferromagnetic Phases for Half-Doped Manganites

Using a two-orbital DE model including the Coulomb interaction, we show that the charge-orbital ordering usually found in the charge-exchange phase may exist in the ferromagnetic phase for half-doped manganites. Thus, two types of phase transitions observed experimentally can be explained by the obtained phase diagram.

Effective Dielectric Properties of an Array of Multishell Carbon Nanotubes

Using a photonic band calculation method, we calculate the effective dielectric function of an array of carbon nanotubes which have a simple equivalent isotropic dielectric function. The results for the equivalent dielectric function and for the local graphite-like dielectric tensor are found to be almost the same. Taking a fixed outer diameter of the nanotubes to be 10 nm and a fixed distance between them to be 10.3 nm, we investigate the effect of the hollow core and found that it is important that the ratio of the inner to the outer radii is approximately larger than 0.3. By taking a large ratio of 0.58, the theoretical results are improved greatly and can describe the experimental data very well.

Control of Semiquantum Chaos by the Nonfeedback Method

We numerically study the dynamic behaviour of coupled chaotic oscillators in a so-called semiquantum chaotic system in which one is classical and the other is quantum mechanical. Fourier spectra of the classical oscillator and the ground-state wavefunction of the quantum part have been investigated, when small pulse perturbations are applied. It is found that semiquantum chaos can also be successfully controlled by the nonfeedback method.