有限温度下Na4团簇的一种新的运动模式：赝传动

在紧密结合的分子动力学基础上,对具有Ｄ２ｈ对和性的Ｎａ４团簇的势力学行为随温度的变化进行了研究。发现在Ｔ〉２００Ｋ时,Ｎａ４团簇产生一种新的运动模式－赝转动。通过研究赝转动时团簇系统热能的变化,提取了Ｎａ４发生转动的势垒为０．０２３ｅＶ。     

有限温度下Na_4 团簇赝转动的局域Lyapunov指数研究

:在紧束缚分子动力学模型基础上,对具有D2h对称性的Na4团簇在不同温度T=76K、112K、212K和224K下的热力学行为进行了研究。根据局域Lyapunov指数分布的变化,对由温度T=76K、112K向温度T=212K、224K的变化中会出现的赝转动所表现的混沌现象进行了分析     

Na5, Na6和Na7团簇光学吸收谱的理论研究

以含时密度泛函理论为基础,结合从头赝势方法运用含时局域密度近似计算了Na5,Na6和Na7团簇的动力学极化强度,并通过傅里叶变换得出了团簇的光学吸收谱.研究表明,计算结果可以较好地再现实验谱,而且Na6和Na7团簇的结果和组态相互作用的结果符合较好.二维结构和三维结构的Na6团簇的计算结果表明,只有二维结构可出现低于2 eV以下的峰,而且二维结构光谱的计算结果与实验结果符合较好.     

Na_mSi_(7-m)(m≤6)团簇的结构和电子性质的密度泛函理论研究

采用密度泛函理论(DFT)在B3LYP/6-311 G(d)水平上,对NamSi7-m(m≤6)团簇的最低能量结构和电子性质进行了研究.结果表明:m≤4时,团簇的稳定结构倾向于Na原子附着在带负电的Si7-m结构的不同位置上,Na原子成分较多时(m≥4)混合团簇的稳定几何结构发生较大的变化,且团簇中Nam的结构与单一的Nam团簇的稳定结构不同;自然电荷布居分析表明,电荷从Na原子转移到Si原子;随着Na原子成分的增加,团簇越来越容易失去电子,且团簇的稳定性也随之减弱;随着m的增加能隙出现振荡,其中Na5Si2的能隙最小,化学活性最强,Na2Si5的能隙最大,化学活性最弱.     

几何构型不同的Na团簇碰撞动力学研究

采用距离相关紧密束缚的分子动力学模型,在不同碰撞能量以及不同的碰撞参数下,研究了两种构型的Na6(2D),Na6(3D)与Na8团簇间的碰撞.讨论了反应机制的变化,即全融合、深度非弹、非弹性碰撞过程.结果表明:构型不同的团簇与相同的靶碰撞显示了不同的特征.低能时Na6(3D)易融合;DIC反应时,易于形成大的团簇 关键词： Na团簇 原子团簇碰撞 紧束缚模型     

第一性原理对XMg_n(X=K,Na,n=1-12)团簇结构与性质的研究

本文基于第一性原理的广义梯度近似GGA下对XMgn(X=K,Na,n=1-12)团簇的结构与性质进行了研究.通过对结构、束缚能、二阶能量差分和劈裂能的分析发现:KMgn(n=1-12)团簇在n5时,其几何结构转变为笼状;在n=12时,K原子进入到团簇的内部且呈逃逸的趋势;KMgn(n=1-12)团簇的相对稳定性在n=6,9时增强;对于Na Mgn(n=1-12)团簇,在n6时,团簇的结构相对简单;在n大于等于6时,团簇的结构呈现出比较复杂的立体结构;Na Mgn(n=1-12)团簇在n=6,9时团簇的相对稳定性增强;最后对比分析KMgn,Na Mgn(n=1-12)的二阶能量差分和劈裂能发现;在n=6时,两种团簇的相对稳定性都较强,但KMg6团簇的稳定性优于Na Mg6团簇.     

钠原子团簇相变的多极形变特征

运用距离相关紧密结合的分子动力学模型,通过无量纲的形变参数S1对简单金属原子团簇Na4、Na8、Na14和Na20相变时的多极形变特征进行了分析,发现S1可以用作表征团簇形变的灵敏探针.     

有限温度下Aa4团簇赝转动的局域Lyapunov指数研究

在紧束缚分子动力学模型基础上,对具有Ｄ２ｈ对称性的Ｎａ团簇在不同温度Ｔ＝７６Ｋ、１１２Ｋ、２１２Ｋ和２２４Ｋ下热力学行为进行了研究。根据局域Ｌｙａｐｕｎｏｖ指数分布的变化,对由温度Ｔ＝７６Ｋ、１１２Ｋ向温度Ｔ＝２１２Ｋ、２２４Ｋ的变化中会出现的赝转动所表现的混沌现象进行了分析。     

Na5, Na6和Na7团簇光学吸收谱的理论研究

以含时密度泛函理论为基础，结合从头赝势方法运用含时局域密度近似计算了Na₅，Na₆和Na₇团簇的动力学极化强度，并通过傅里叶变换得出了团簇的光学吸收谱.研究表明，计算结果可以较好地再现实验谱，而且Na₆和Na₇团簇的结果和组态相互作用的结果符合较好.二维结构和三维结构的Na₆团簇的计算结果表明，只有二维结构可出现低于2 eV以下的峰，而且二维结构光谱的计算结果与实验结果符合较好. 关键词： 光吸收谱 Na团簇 含时局域密度近似     

第一性原理对NaBen(n=1—12)团簇最低能量结构及其电子性质的研究

从第一性原理出发对NaBe_n(n=1—12)团簇的最低能量结构和电子性质进行了研究.结果表明，掺杂原子(Na)导致主团簇Be_n的几何结构发生显著变化；出现了共价键和金属键的成键特性；Na-Be最近邻间距和能隙随着团簇尺寸的增加出现了振荡;n=4是团簇的幻数. 关键词： n团簇')" href="#">NaBe_n团簇 最低能量结构 电子性质     

A Pseudo-Stokes Mesh Motion Algorithm

This work presents a moving mesh methodology based on the solution of a pseudo flow problem. The mesh motion is modeled as a pseudo Stokes problem solved by an explicit finite element projection method. The mesh quality requirements are satisfied by employing a null divergent velocity condition. This methodology is applied to triangular unstructured meshes and compared to well known approaches such as the ones based on diffusion and pseudo structural problems. One of the test cases is an airfoil with a fully meshed domain. A specific rotation velocity is imposed as the airfoil boundary condition. The other test is a set of two cylinders that move toward each other. A mesh quality criterion is employed to identify critically distorted elements and to evaluate the performance of each mesh motion approach. The results obtained for each test case show that the pseudo-flow methodology produces satisfactory meshes during the moving process.     

Two-dimensional modeling and simulation for dynamic sheathexpansion during plasma immersion ion implantation

A pseudo two-dimensional (2-D) analytical model and a 2-D plasma simulator PDP2 code have been utilized to characterize ion-matrix sheath and dynamic sheath expansion during the plasma immersion ion implantation process. The pseudo 2-D model is very simple by involving two geometry factors and yields an acceptable accuracy under the current process conditions. Good agreement between the pseudo 2-D model and PDP2 simulation was observed     

块二级多分裂预条件迭代方法

提出一种块二级多分裂PE迭代算法(TSMPE),可以克服M^-1r^(s)并行化处理的困难。     

Neutron spin rotation and P-violation

A new apparatus to measure the neutron spin rotation due to interaction with matter has been developed at KEK. The present apparatus enables us to measure the parity violating neutron spin rotation in the p-wave resonance in the energy region of eV.On leave from Tohoku University.     

Pseudo topological insulators

We predict pseudo topological insulators that have been previously overlooked. We determine some conditions under which robust pseudo topological edge states appear and illustrate our idea on the Su–Schrieffer–Heeger (SSH) model with extra chiral symmetry breaking potentials. We discuss that pseudo topological insulating phase transition occurs without band gap closing.     

声子角动量与手性声子

在经典的物理学理论中,声子广泛地被认为是线极化的、不具有角动量的.最近的理论研究发现,在具有自旋声子相互作用的磁性体系(时间反演对称性破缺)中,声子可以携带非零的角动量,在零温时声子除了具有零点能以外还带有零点角动量;非零的声子角动量将会修正通过爱因斯坦-德哈斯效应测量的回磁比.在非磁性材料中,总的声子角动量为零,但是在空间反演对称性破缺的六角晶格体系中,其倒格子空间的高对称点上声子具有角动量,并具有确定的手性;三重旋转对称操作给予声子量子化的赝角动量,赝角动量的守恒将决定电子谷间散射的选择定则;此外还理论预测了谷声子霍尔效应.     

Translation–rotation coupling in the self–diffusion of fluids: molecular dynamic investigation and a generalized exponential approach

Detailed molecular dynamics simulations are carried out to investigate the translation–rotation coupling in linear molecules. We calculated the moment of inertia ratio dependence of the self–diffusion coefficients D, the so–called dynamic isotope effect on the self–diffusion, in pure fluids. Our model systems consist of linear homonuclear pseudo–triatomic rigid molecules for three different molecular sizes over a wide range of density for a given temperature. For a compact representation of our results an exponential approach is employed, which demonstrates a strong translation–rotation coupling on the self–diffusion coefficient in a linear molecule. We find as a main result that in contrast to the low density behaviour at high densities the change of the rotation–translation coupling as a function of the moments of inertia is quite similar for all investigated molecules and we could explain this finding by a careful inspection of the corresponding velocity autocorrelation functions. Finally we present a comparison of experimental data for 20 neat molecular liquids and the corresponding theoretical predictions based on our findings for linear molecules. The good overall agreement indicates that our approach can be generalized and is therefore not only a compact representation of the calculated data but has also large predictive capabilities.     

Calculation of photoionization cross sections by the absorbing boundary method

A new method for the calculation of quantum state decay rates, the absorbing boundary method (ABM), has recently been developed. In this talk the general form of the ABM will be outlined. The pseudo bound state approach to the calculation of continuum rates such as photoionization cross sections and used by Langhoff and coworkers will be briefly reviewed and shown to lack precision in the absence of information about the line widths and shapes of the pseudo bound states. It will then be noted that the ABM can be used to construct a rigorous new approach to the calculation of photoionization cross sections incorporating the necessary lifetime information for the pseudo bound states while still allowing the computation to be carried out by bound state procedures.     

晶格旋转对称性的单转轴证明

传统的晶格旋转对称性的双转轴证明方法不满足旋转对称操作至少要保持一点不动的要求，本文提出了晶格旋转对称的单转轴证明方法，克服双转轴证明方法的缺点。     

激光场中H原子多光子电离速率

建立了激光与原子相互作用的伪分立态模型,并用此模型计算了激光场中Ｈ原子的多光子电离速率。对于光子能量较小的激光,计算结果与其它理论计算结果相符合。