On the chemisorption of hydrogen on lithium clusters

Ab-initio Hartree-Fock calculations for hydrogen atoms chemisorbed on lithium clusters have been performed using a basis which includes p-functions. No penetration of the hydrogen atom beyond the surface of the cluster was observed. The distance between the hydrogen atom and the nearest lithium atoms of the cluster becomes larger as the coordination number increases.     

锂原子的高激发态能级计算及其在微波场中的布居动力学过程

利用B样条技术,设计了一种计算高激发原子能级结构的方法,计算了高激发锂原子的能级结构,并研究了里德堡锂原子在微波场中的布居动力学过程。     

激光场中锂原子发射的电离阈值以下低阶谐波的研究

利用单电子近似下锂原子精确的模型势,通过数值求解三维含时薛定谔方程的方法,研究了锂原子在激光场中发射低阶谐波的性质,研究结果表明,对于锂原子电离阈值以下的低阶谐波,除了通常的奇次谐波外,还有侧峰结构出现,运用同步压缩变换技术(SST)分析这些低阶谐波的辐射特性,我们发现这些侧峰是由原子在激光场中的缀饰态之间的跃迁和无场下激发态到基态的跃迁组成的,如果当激光脉冲结束后,仍有发射的侧峰,其位置与主峰之间的能量差可以用来估算原子激发态在激光场中的最大Stark移动.     

Polarizabilities and Hyperpolarizabilities for Lithium Atoms in Debye Plasmas

The effects of plasma environments on energies, oscillator strengths, polarizabilities and hyperpolarizabilities for lithium atom have been calculated by combining the l-dependent model potential of free lithium atom and linear variation method based on B-spline basis functions. The influence of plasma on lithium atom is represented by the Debye screened potential, which describes effectively the averaged effect of the plasma environment on atomic spectra. The results are in agreement with other reported ones.     

Influence of impurity hydrogen on the structure and properties of bulk Li and pressure effects

The structure and properties of a 16-atom body-centered cubic lithium cell with an interstitial hydrogen atom are studied using a pseudopotential-plane-wave method within the density functional theory at 0 K and high pressures. The host lattice is dramatically distorted by the introduction of H. Although the hydrogen atom is stable at the tetragonal site in perfect bcc host lattice, it favors the octahedral site formed by six non-equivalent Li atoms after full relaxation of the cell, showing P4/mmm symmetry within the pressures ranging from 0 to 6 GPa. The lattice ratio (a/c) changes irregularly with external pressure at about 3 GPa. The hydrogen band lies in the bottom of the valence band, separated by a gap from the metallic bands, illustrating the electronegativity of hydrogen. High reflectivity in the low frequency area induced by the impurity hydrogen is observed when only interband transitions are taken account of. A dip in reflectivity due to parallel band transitions is observed at ∼0.4 eV. Another dip at ∼4.3 eV appears when external pressure increases over 4 GPa.     

微波场中里德堡锂原子的高激发跃迁

运用含时多态展开方法研究微波场中里德堡锂原子高激发态的性质,得到锂原子在微波场中的跃迁几率,实现对量子态的操纵与控制。结果表明：选择合适的振幅、频率等参数,可以实现布居数在量子态之间的完全跃迁。     

Electron-nuclear entanglement in the cold lithium gases

We study the ground-state entanglement and thermal entanglement in the hyperfine interaction of the lithium atom. We present the relationship between the entanglement and both temperature and external magnetic fields.     

Many-body calculation of dynamic quadrupole polarizability and related properties of lithium

Dynamic quadrupole polarizability of lithium atom has been calculated in its ground state using linked cluster many-body perturbation theory. Van der Waals constants have been calculated for dipole-quadrupole and quadrupole-quadrupole interactions of lithium atoms with helium and other lithium atoms. The results compare well with other available values.     

难熔元素钨在NiAl位错体系中的占位及对键合性质的影响

用第一性原理离散变分方法研究了难熔元素钨(W)在金 属间化合物NiAl<100>(010)刃型位错体系中的占位以及对键合性质的影响, 计算了纯位错体系和掺杂体系的能量参数(结合能、 杂质偏聚能及原子间相互作用能)、 态密度和电荷密度分布. 体系结合能和杂质偏聚能的计算结果表明: 难熔元素W优先占据Al格位. 此外,由于难熔元素W的4d轨道与近邻基体原子Ni的3d轨道和Al的3p轨道的杂化, 使得掺杂体系中难熔元素W与近邻基体原子间的相互作用能加强; 同时难熔元素W与位错芯区近邻基体原子间有较多的电荷聚集, 这表明W与近邻基体原子间形成了较强的化学键. 难熔元素W对NiAl化合物的能量及电子结构有较大的影响, 从而影响位错的运动及NiAl金属间化合物的性能. 关键词： 电子结构 位错 金属间化合物 杂质     

Absorption and Recurrence Spectra of Nonhydrogenic Rydberg Atom Near a Metal Surface

Multielectron to theoretical treatments atoms near a metal surface are essentially more complicated than hydrogen atom with regard By using the semicalssical dosed orbit theory generalized to the multielecton atoms, we study the dynamical properties of the Rydberg lithium atom near a metal surface. The photoabsorption spectra and recurrence spectra of this system have also been calculated. Considering the effect of the ionic core potential of the Rydberg lithium atom, the number of the closed orbits increases, which leads to more peaks in the recurrence spectra than the case of hydrogen atom near a metal surface. This result shows that the core-scattered effects play an important role in nonhydrogenic atoms. This study is a new application of the closed-orbit theory and is of potential experimental interest.     

锂原子里德伯态能级的精细结构分裂

对锂原子的四体问题的哈密顿算符进行幂级数展开,通过计算原子实的 极化(包括偶极矩,四极矩至八级电极矩)对能级的贡献,同时考虑相对论效应和LS耦合以 及有效势的高阶修正,求得了锂原子里德伯态的能级位移和能级公式。用此公式计算N=5～1 2,L=4～9,J=L±1/2的相关的精细结构位移以及能级间隔,并与有关实验结果进行了比较 。     

锂里德堡态的d-f间隔的共振计算

应用全实加关联方法计算而得到的锂原子的1s2nd (n=3–5) 态 和 1s2nf (n=4–6) 态的能量，我们可以通过量子亏损理论得到量子亏损函数，它随着能量平缓地变化。利用这些函数可以分别构造一个系统方程去求解锂原子1s2nd和 1s2nf (n=7–11)里德堡态的能量和量子亏损。我们计算了nd和nf 中心能级 (n=7–11)的间隔并和文献中已有的实验和理论数据做了比较。     

热锂束荧光探测电子密度

使用基于锂原子与电子碰撞激励产生荧光以测量电子密度的新方法,并用CCD摄象机和S20光电倍增管同时观察了锂原子6708?(²P⁰—²S)的荧光信号,并从光强分布曲线推算出电子密度的径向分布。 关键词：     

甲醇锂和乙醇锂拉曼光谱的密度泛函理论研究

前人研究证明在烷氧基锂(ROLi)中锂原子直接和氧原子相连而形成O-Li健,作者依此构造出甲醇锂和乙醇锂的分子构型.目前在实验和理论计算上都尚无对甲醇锂和乙醇锂分子的拉曼光谱的报道.文章用密度泛函珲论中的B3LYP混合泛函联合6-31G(d,p)基函数组进行了这两个分子的结构优化得到其平衡构型.基于此平衡构型计算出甲醇锂和乙醇锂的振动频率和拉曼光谱,对计算所得的振动频率进行了简正坐标分析,根据各频率的势能分布进行了全面的归属指认,旨在为用拉曼光谱技术研究和分析锂离子电池固体电解质膜(SEI膜)组分提供更多的理论依据.     

Formation Mechanism and Binding Energy for Regular Tetrahedral Structure of Li4

The formation mechanism for the regular tetrahedral structure of Li4 cluster is proposed. The curve of the total energy versus the separation R between the two nuclei has been calculated by using the method of Gou＇s modified arrangement channel quantum mechanics （MACQM）. The result shows that the curve has a minimal energy of-29.8279 a.u. at R = 14.50 ao. When R approaches infinity the total energy of four lithium atoms has the value of-29.7121 a.u. So the binding energy of Li4 with respect to four lithium atoms is the difference of 0.1158 a.u.for the above two energy values. Therefore the binding energy per atom for Lh is 0.020 a.u., or 0.7878 eV, which is greater than the binding energy per atom of 0.453 eV for Li2, the binding energy per atom of 0.494 eV for Lia and the binding energy per atom of 0.632 eV for Li5 calculated previously by us. This means that the Li4 cluster may be formed stably in a regular tetrahedral structure of side length R = 14.50 ao with a greater binding energy.     

Formation Mechanism and Binding Energy for Body-Centred Regular Octahedral Structure of Li7 Cluster

The formation mechanism for the body-centred regular octahedral structure of Li7 cluster is proposed. The curve of the total energy versus the separation R between the nucleus at the centre and nuclei at the apexes for this structure of Li7 has been calculated by using the method of Gou＇s modified arrangement channel quantum mechanics （MACQM）. The result shows that the curve has a minimal energy of-52.169 73 a.u. at R = 5.06ao. When R approaches infinity, the total energy of seven lithium atoms has the value of-51.996 21 a.u. So the binding energy of Li7 with respect to seven lithium atoms is 0.173 52 a.u. Therefore the binding energy per atom for Li7 is 0.024 79 a.u. or 0.674 eV, which is greater than the binding energy per atom of 0.453 eV for Li2, the binding energy per atom of 0.494 eV for Li3 and the binding energy per atom of 0.632 eV for Li5 calculated previously by us. This means that the Li7 cluster may be formed stably in a body-centred regular octahedral structure with a greater binding energy.     

Theoretical study of the diffusion of lithium in crystalline and amorphous silicon

The effect of the lattice deformation on potential barriers for the motion of a lithium atom in crystalline silicon has been studied through ab initio density functional calculations. A new universal method of calculating the diffusion coefficient of an admixture in amorphous solid media through the activation mechanism has been proposed on the basis of these data. The method is based on the calculation of the statistical distribution of potential barriers for the motion of an admixture atom between minima depending on the position of neighboring atoms. First, the amorphous structure, which is generated by annealing from the crystalline structure with vacancies, has been simulated. Then, the statistical distribution of the potential barriers in the amorphous structure for various local environments of the admixture atoms has been calculated by means of linear regression with the parameters determined for barriers in crystalline silicon subjected to different deformations. The diffusion coefficient of the admixture has been calculated from this distribution by using the Arrhenius formula. This method has been tested by the example of crystalline and amorphous silicon with admixture of lithium atoms. The method demonstrates that the diffusion of lithium in amorphous silicon is much faster than that in crystalline silicon; this relation is confirmed experimentally.     

Surface complexes between O2, H2O and lithium

The He(I) photoelectron spectra of lithium and its surfaces as a function of exposure to O₂ or to H₂O are reported in this paper. The spectra provide evidence for the formation of a stable complex between H₂O and lithium rather than for formation of a product such as LiOH. The spectral evidence for the H₂O/Li complex is supported by calculations using several ten atom models of binding sites on unreconstructed lithium surfaces bearing H₂O in various conformations.     

啁啾微波场中里德伯锂原子的相干激发与控制

运用含时多态展开方法和B-样条函数研究了微波场中里德伯锂原子高激发态的性质,得到锂原子量子态n=70-75,l=0-5的能量,并分析了里德伯锂原子高激发态n=70-75,l=0-5在微波场中的跃迁几率.结果表明:通过优化微波场参数可以实现量子系统从初始态到目标态的完全跃迁,且在跃迁过程中,每个l态都起至关重要的作用.     

Formation Mechanism and Binding Energy for Regular Octahedral Structure of Li6 Cluster

The formation mechanism for the regular octahedral structure of Li₆ cluster is proposed. The curve of the total energy versus the separation R between any two neighboring nuclei has been calculated by using the method of Gou's modified arrangement channel quantum mechanics (MACQM). The result shows that the curve has a minimal energy of -44.736 89 a.u. at R = 5.07a₀. When R approaches infinity, the total energy of six lithium atoms has the value of -44.568 17 a.u. So the binding energy of Li₆ with respect to six lithium atoms is 0.1687 a.u. Therefore, the binding energy per atom for Li₆ is 0.028 12 a.u., or 0.7637 eV, which is greater than the binding energy per atom of 0.453 eV for Li₂ and the binding energy per atom of 0.494 eV for Li₃ calculated in our previous work. This means that the Li₆ cluster may be formed in a regular octahedral structure with a greater binding energy.