Structural and vibrational properties of deformedcarbon nanotubes

The fantastic variation of the physical properties of carbon nanotubes (CNTs) and their bundles under mechanical strain and hydrostatic pressure makes them promising materials for fabricating nanoscale electromechanical coupling devices or transducers. In this paper, we review the recent progress in this field, with much emphasis on our first-principles numerical studies on the structural and vibrational properties of the deformed CNTs under uniaxial and torsional strains, and hydrostatic pressure. The nonresonant Raman spectra of the deformed CNTs are also introduced, which are calculated by the first-principles calculations and the empirical bond polarizability model.     

金属双层膜中量子输运的表面和界面散射效应

运用格林函数的解析方法研究金属双层膜的电子输运.考虑了量子尺寸效应和来自杂质、粗糙表面和粗糙界面三方面的散射,计算单粒子格林函数和平行电导率,得到了金属双层膜的电导公式.计算结果表明,在薄膜极限和表面及界面散射的最低阶近似下,系统总电导率等于各子能级通道的电导率之和,而各子能级通道中杂质、表面和界面产生的散射率是可相加的. 关键词：     

金属薄膜的量子输运理论

运用格林函数方法和久保公式研究金属薄膜中的电子输运．考虑了量子尺寸效应及来自杂质和两个粗糙表面的散射，计算单粒子格林函数和平行电导率．计算结果表明：（1）在薄膜系统中，电子数密度、平均自由程以及来自杂质和表面散射的电导率都以π/k_F（k_F为费密波矢的数值）为周期随厚度d振荡；（2）在薄膜和厚膜的两种极限、以及取表面粗糙度的最低阶近似下的结果可以推出用半经典和量子方法所得的金属薄膜的电导公式 关键词：     

铁磁-绝缘层-d波超导结中的Andreev反射特性

考虑到铁磁层中的磁交换作用和界面散射效应,利用推广的Blonder-Tinkham-Klapwijk散射理论,计算铁磁-绝缘层-d波超导结中的准粒子输运系数与隧道谱.研究表明：铁磁层中的交换场能抑制Andreev反射,使得依赖于准粒子入射角的Andreev反射表现出瞬息波的行为,呈现一些新的隧道谱特征. 关键词： Andreev反射 d波超导 隧道谱     

轨道序对半掺杂锰氧化物光学性质的影响

在两轨道双交换模型基础上，讨论了电子关联作用对半掺杂锰氧化物轨道序的影响，推导出能计算各个相的光电导公式.结果显示，光吸收与轨道序之间存在关联现象.对于铁磁相，当格点库仑相互作用(U)从无到有逐渐增加时，铁磁相会从无轨道序过渡到有轨道序，相变前 后非相干光吸收有一个从无能隙到有能隙的明显变化.对于层状反铁磁的A相，U的增加会使 轨道序更明显，非相干光吸收部分的能隙随之也增大. 关键词： 轨道序 光电导 锰氧化物 库仑相互作用     

EXTENDED SSH MODEL FOR C58B2 AND C58N2

The extended Su-Schrieffer-Heeger model is used to study the electronic energy levels and molecular structures for two kinds of isomers of C₅₈X₂(X=B, or N). In each case we obtain two sets of stable solutions. For C₅₈X₂ (1, 2), both sets of solutions are found to be reasonable, indicating two different phases. For C₅₈X₂(1, 60 ), only one set of solutions which satisfy the central inversion symmetry is physically reasonable.     

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

The heat transport m a one-dimensional （ID） 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 k- N, in which a 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 a value.     

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.     

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.     

替位式掺杂的富勒烯分子C77X(X=B,N原子)的非线性光学性质

采用推广的Su-Schrieffer-Heeger模型和sum-over-state方法计算了掺杂的富勒烯分子C₇₇X(X=B或N原子)的三阶非线性极化率γ.计算结果表明：1)与C₇₈相比,各C₇₇X分子的三阶非线性极化率γ的静态值均有不同程度的提高(3—40倍);2) C₇₇X的非线性动态光学响应不仅与掺杂原子有关,还与异构体种类和掺杂位置有关. 关键词：