基于一维紧束缚SSH 模型和扩展的 Hubbard模型，采用非绝热分子动力学方法，在非限制性 Har-tree-Fock（HF）平均场近似下，研究了三粒子复合体 trion的静态性质．trion比极化子、双极化子具有更大的束缚能、稳定性和有效质量；电子声子耦合和电子间相互作用均增强 trion的局域度，并导致其有效质量增大，稳定性增强．

Based on the one-dimensional tight-binding Su-Schrieffer-Heeger (SSH ) model and the ex-tended Hubbard model(EHM ) ,using an nonadiabatic molecular dynamics method ,the static properties of trions in conjugated polymers at the unrestricted hartree-fock(UHF) level was investigated .Trion posses-ses the larger binding energy ,stability and effective mass than those of both the polaron and the bipolaron . The electron-electron and electron-phonon interactions all strengthen the localization ,effective mass and stability of the trion .

基于一维紧束缚的Su-Schreiffer-Heeger模型,采用非绝热动力学方法,研究了链间耦合对聚合物中极化子对非弹性散射性质的影响:激子的产生依赖于链间耦合,随着耦合强度的增加,正负极化子对的电子波函数交叠增强,利于提高激子的产率;当耦合区域是极化子的宽度时,正负极化子对波函数的耦合最充分、耦合最强,电荷跃迁更容易,激子产率最大.

@@@@Within an one-dimensional tight-binding Su-Schreiffer-Heeger model, we investigate the effect of interchain coupling on inelastic scattering of oppositely charged polarons in conjugated polymer by using a nonadiabatic evolution method. It is found that the yield of the neutral exciton depends sensitively on the interchain coupling. The yield of the neutral exciton increases with the enhancement of overlapping which can make the wave functions of oppositely charged polarons more largely overlapped. The formation yield of excitons also increases with the number of overlapping sites increasing to its maximum value, where the length of overlapping sites is almost of the same order of magnitude as the width of the polaron, the reason is that the number of overlapping sites can affect the overlap of oppositely charged polaron wave functions. In turn, the charge transfer between them depends on the overlap of their wave functions. Therefore, when the size of overlapping sites is almost of

将两种全局结构搜索方法(压缩液态法、遗传算法)与锗的紧束缚势模型相互结合,对Ge65, Ge70, Ge75的稳定结构进行了大规模的搜寻，提出能量较低的可能结构,然后进一步利用第一性原理方法对这些低能结构进行精确的优化计算,确定出了这三种尺寸团簇的基态结构。发现这三种团簇各具有两种稳定的并且能量相近的异构体：类球形和类椭球形,这与实验上报道的大尺寸团簇Gen (65 n 80)的结构特征相符合。简要地分析了这三种团簇基态结构的电子性质。

The low-lying candidates of Ge65, Ge70 and Ge75 are extensively investigated through combining the tight-binding potential of germanium with two kinds of global minima search strategies:compressing liquid and genetic algorithm. Then, we perform accurate ab initio calculations to optimize the atomic structures of these low-lying candidates and identify the ground state structures. Our calculations predict that there exist two kinds of stable isomers characterizing the sphere-and ellipsoid-like structural features for each sized cluster, and the two kinds of isomers are energetically competitive. This is consistent with the observation for the large sized clusters Gen (65 n 80) in experiment. Meanwhile, we also briefly analyze the electronic properties of these three kinds of clusters.

采用紧束缚模型分别描述单层、双层石墨烯的能带结构,利用光子-电子相互作用的二阶微扰理论分别计算单光子和双光子吸收系数.计算结果表明:单层石墨烯单光子吸收系数为常数,约为6.8×107m 1,即单层石墨烯对入射光的吸收率约为2.3%;双层石墨烯的单光子吸收比单层石墨烯的单光子吸收强,且随入射光波长呈分段性变化.单层石墨烯的双光子吸收系数与波长λ4成正比;双层石墨烯双光子吸收系数在红外波段(~3100 nm处)有一个很强的共振吸收峰.研究结果可为石墨烯材料在光电子器件的研究和制作方面提供指导.

We theoretically simulate one-photon and two-photon absorption spectra for monolayer and bilayer graphene employing the second-order perturbation theory of the electron-photon interaction. The tight-binding model is used to describe the band structure of graphene. The results show that one-photon absorption coefficient of monolayer graphene is a constant about 6.8 × 107 m?1, demon-strating that the absorptivity of incident light in monolayer graphene approximates to 2.3%. The one-photon absorption coefficient of bilayer graphene changes sectionally with the wavelength and is greater than that of monolayer graphene. The two-photon absorption coefficient of monolayer graphene is proportional toλ4 . The two-photon absorption coefficient of bilayer graphene exhibits a giant resonance absorption peak in the infrared (～3100 nm) region. Our results will provide theoretical guidance for the application of graphene in the research field of optoelectronic devices.

基于紧束缚近似哈密顿模型,运用波包动力学方法,数值模拟研究了石墨烯电子穿越线缺陷的输运性质和相应的透射率,着重探讨线缺陷对于电子Valley赝自旋的滤波特性.模拟结果表明:(1)石墨烯线缺陷对于电子valley赝自旋具有半透性;(2)电子的透射率与入射角度和能量都有关;(3)在某个临界角度θc,透射率出现峰值,其大小随着能量的增加而增大,而|θc|的绝对值却随能量的增加而减小;(4)当入射角|θ|大于|θc|时,透射率将急剧地降为0.进一步的理论分析指出,这是由于透射率能量关系中的非线性项所造成的.最后,我们的数值模拟结果进一步地证明了石墨烯线缺陷未来作为valley赝自旋滤波器件的实用可能性.

Graphene is a promising nanostructure material used in the field of materials science,electronics and nanotechnology because of its unique geometric structure and amazing physical and chemical properties.In addition to the conventional spatial and spin degrees of freedom,the electrons in graphene have another degree of freedom,called as the valley pseudospin,making it possible to develop the specific valleytronics devices by the graphene,which are very similar to those in the spintronics.However,the pristine graphene is a zero-gap semiconductor,which brings a great difficulty to the control of graphene electron and limits its potential applications in the field of nano-electronic devices.In order to solve this problem,the method to produce some defects in the grapheme is often used.Recently,the topological defects in graphene, such as the grain boundary and line defect,have been observed in experiments,which will have a big effect on its electronic transport properties,e.g.,changing th