二维Fibonacci准晶电子能谱

基于重整化群技术,我们用分解-消元方法研究二维Fibonacci准晶电子能谱性质,得到了具有多种分支结构的能谱,这与一维Fibonacci的单一分支结构完全不同。同时,利用晶格的四重旋转对称性将哈密顿量化简,然后进行数值模拟计算,计算结果与分析结果完全一致。 关键词：     

按斐波那契类准周期序列排列的铁电畴超晶格二次谐波谱峰性质研究

在简介斐波那契类(Fibonacci-class)准晶(FC(n))的特征基础上,在小信号、平面波近似下详细地研究了通过N层按斐波那契类准周期系列排布的铁电畴超晶格的二次谐波光场的谱性质.发现其谱的极强峰在实空间,在不考虑介质色散效应的情况下,具有完美的自相似性;对于具有线性色散效应的铁电晶体,其谱在实空间也具有相同的结论;而对于具有非线性色散效应的铁电介质,极强峰的这种自相似性将被破坏.另外,二次谐波光的暗线处将存在缺级效应;亮线处则无缺级效应. 关键词：     

广义Fibonacci准周期链能谱性质

本文研究一种广义Fibonacci准周期链(孪生子模型)的电子及声子谱。重整化群分析表明,电子能谱具有3分支的自相似结构,但每一层中的中间子带又类似于周期系统。数值计算结果证明这种分析的正确性。对于声子谱,则显示出与Fibonacci链相同的性质。 关键词：     

无序一维无公度调制链的电子结构

本文用数值方法分别研究了替代型无序和周期无序对一维准周期系统电子结构的影响。两种类型的无序都将破坏准周期系统的Cantor集合型的能谱结构,但前者会在原有的禁带处产生杂质能级,后者主要引起原有能带轮廓的展宽。 关键词：     

一族一维准晶的局部电子性质

本文利用推广的实空间重整化群方法,研究按膨胀规则(A,B)→(AⁿB,A)构造的一族一维泛Fibonacci准晶系(A_n序列)的局部电子性质。所引入的2n²+1种基本变换可计算该族一维准晶中任一A_n序列在任意格点的局部格林函数和局部态密度。结果表明,该方法是有效的,A_n链的电子局部态密度象Fibonacci准晶一样,呈现临界性。 关键词：     

用无源电路实现斐波那契数列

斐波那契数列具有许多有趣的性质,广泛见于理论分析和实际应用中。电容器、电感器和电阻器是电路中基本的无源元件。本文应用基尔霍夫定律对梯形结构的纯电容和纯电阻网络进行了分析,指出它们可以清晰而简洁地实现斐波那契数列,并给出了斐波那契数列的若干性质在电阻电路中的反映和体现。最后用电路仿真软件和实际电路给出具体的测量数值,结果与理论分析完全一致。     

n分量φ4模型薄膜的尺寸效应

我们用场论重整化群方法讨论了周期边界的n分量φ⁴模型薄膜的单纯尺寸效应,发现仅当维数满足d_<+1>时尺寸效应具有Fisher的标度形式,其他情况下它是不可标度的。同时也讨论了维数渡越现象及状态方程。 关键词：     

Ni-Cr非中心对称准晶的电子性质

在单电子、紧束缚和最近邻相互作用条件下，本文利用迁移模型分析和计算了单种原子、单键长的二维十二次准晶的电子性质，包括电子能谱、积分态密度和判断电子波函数局域性的一阶矩、二阶矩、反参加比等参数。我们发现电子能谱没有正常简并，只有偶然简并，以及电子只有中间态，没有扩展态和局域态。     

离散变分x_α的双电子计算及MgF_2Ni~(2+)的晶场能级

使用离散变分x_a双电子计算方法计算了激光晶体MgF_2:Ni~(2+) 的部分双电子积分,并由此获得晶体的单态和三重态分裂值.结合离散变分x_a自旋计算,获得了MgF_2:Ni~(2+)的晶场能级.     

Ni—Cr非中心对称准晶的电子性质

在单电子、紧束缚和最近邻相互作用条件下，本文利用迁移模型分析和计算了单种原子、单健长的二维十二次准晶的电子性质，包括电子能谱、积分态密度和判断电子波函数局域性的一阶矩、二阶矩、反参加比等参数。我们发现电子能谱没有正常简并，只有偶然简并，以及电子只有中间态，没有扩展态和局域态。     

Splitting rules for the electronic energy spectra of 2D FC(n) with three kinds of atoms and one bond length

In this paper we study the splitting rules of energy spectra for two-dimensional Fibonacci-class quasilattices (FC(n)) with three kinds of atoms (A, B, and C) and one bond length by means of a decomposition-decimation method, and find that the sublattices of B atoms and C atoms are different from those of normal two-dimensional FC(n) and the corresponding splitting manners are new and interesting. B atom forms a kind of two-dimensional so-called FC(n)’, which structure is some different from that of normal FC(n-1) (n≥2), but the spectra lines are as the same as that of the latter. C atom forms two kinds of interesting one-dimensional periodic chains: n-atom chain and (n-1)-atom chain, which spectra will both tend to become continuous, respectively. The analytical results are confirmed by numerical simulations.     

Splitting rules for the 2nd hierarchy structure of the electronic spectra of 2D FC(n) quasicrystals

On the basis of our former work and by means of the decomposition-decimation method, we study the splitting rules for the second hierarchy of the electronic energy spectra for two-dimensional Fibonacci-class quasicrystals with one kind of atom and two bond lengths. It is found that every line of the sub-spectra for n x n and (n + 1) x (n + 1) clusters of FC(n) splits according to the type Y_(n-1)-2-1 and type Y _n-2-1 respectively. The one for n x (n + 1) clusters of FC(n) consists of three sub-subbands when , and five sub-subbranches when . The general formulae of the number of energy levels for the spectra of the second hierarchy are obtained. The analytical results are confirmed by numerical simulations.Received: 18 March 2004, Published online: 23 July 2004PACS: 71.23.Ft Quasicrystals - 63.90. + t Other topics in lattice dynamics (restricted to new topics in section 63) - 33.70.Jg Line and band widths, shapes, and shifts     

Real space renormalization group approach to the two-dimensional antiferromagnetic Heisenberg model (I) – The singlet triplet gap

The low energy behaviour of the two-dimensional antiferromagnetic Heisenberg model is studied in the sector with total spins S = 0,1,2 by means of a renormalization group procedure, which generates a recursion formula for the interaction matrix Δ_S ⁽ⁿ⁺¹⁾ of 4 neighbouring “n clusters” of size 2ⁿ × 2ⁿ, n = 1,2,3,... from the corresponding quantities Δ_S ⁽ⁿ⁾. Conservation of total spin S is implemented explicitly and plays an important role. It is shown, how the ground state energies E_S ⁽ⁿ⁺¹⁾, S = 0,1,2 approach each other for increasing n, i.e. system size. The most relevant couplings in the interaction matrices are generated by the transitions 〈S’,m’;n+1|S_q ^*|S,m;n+1〉 between the ground states |S,m;n+1〉 (m = -S,...,S) on an (n+1)-cluster of size 2ⁿ⁺¹ × 2ⁿ⁺¹, mediated by the staggered spin operator S_q ^*.     

光在按特殊准晶方式排列的媒质中的传播

简单介绍Fibonacci-class准晶(FC(n))的结构特性，利用电场理论和二阶单位模矩阵的特殊性质，研究了光在按FC(n)准晶链排列的多层介质膜中传播时的光透射性质，发现FC(2m)的透射系数具有开关性质，FC(2m+1)的透射系数具有六循环性质，它们的最大值在π(1/2±k)附近具有有趣的性质. 关键词：     

电子阻止本领Se(E)的z振荡及其计算

本文应用Hartree-Fock-Slater势能代替Thomas-Fermi势能,得出电子阻止本领S_e(E)的归一化关系式;同时,结合有效原子序数概念,得出能量对S_e(E)影响的关系式,利用前一关系式,定量计算了S_e(E)随离子和靶原子的原子序数z变化的振荡关系,计算结果与实验值相当符合,利用后一关系式,定量计算了多种离子-靶体系的S_e(E),与文献[1]的关系式比较,本文结果更好地符合实验值,而且有更广的能量适用范 关键词：     

Deconfinement phase transition in a two-dimensional model of interacting 2 × 2 plaquettes

The low energy behaviour of the two-dimensional antiferromagnetic Heisenberg model is studied in the sector with total spins S = 0,1,2 by means of a renormalization group procedure, which generates a recursion formula for the interaction matrix Δ_S ⁽ⁿ⁺¹⁾ of 4 neighbouring “n clusters” of size 2ⁿ × 2ⁿ, n = 1,2,3,... from the corresponding quantities Δ_S ⁽ⁿ⁾. Conservation of total spin S is implemented explicitly and plays an important role. It is shown, how the ground state energies E_S ⁽ⁿ⁺¹⁾, S = 0,1,2 approach each other for increasing n, i.e. system size. The most relevant couplings in the interaction matrices are generated by the transitions 〈S’,m’;n+1|S_q ^*|S,m;n+1〉 between the ground states |S,m;n+1〉 (m = -S,...,S) on an (n+1)-cluster of size 2ⁿ⁺¹ × 2ⁿ⁺¹, mediated by the staggered spin operator S_q ^*.     

Spectroscopic effects of conical intersections of molecular potential energy surfaces

A simple vibronic coupling model involving two electronic states and two vibrational modes is considered. The model is based on harmonic diabatic potentials and linear coupling of the diabatic electronic states. It is shown that the adiabatic electronic potential energy surfaces exhibit, in general, a conical intersection. The well known E × E and E × B Jahn-Teller problems are contained as special cases. Using numerical methods the optical absorption spectrum is calculated exactly. Extremely complex vibronic spectra are obtained when the conical intersection occurs within the Franck-Condon (FC) zone. The exact vibronic spectra are compared with spectra calculated in the adiabatic and FC approximation. The genuine spectroscopic effects of conical intersections are revealed by a comparison with the results of standard one-dimensional vibronic coupling calculations. The presence of a conical intersection limits the applicability of the adiabatic and FC approximations much more strongly than in the one-dimensional case. The upper adiabatic electronic state is strongly affected by non-adiabatic coupling even when the point of intersection lies outside the FC zone. The relevance of these results for the calculation of molecular electronic spectra is briefly discussed.     

Cu台阶面多层弛豫的第一性原理研究

采用基于密度泛函理论的第一性原理赝势平面波方法对Cu(311),(511),(331)和(221)四个高指数台阶表面的弛豫结构和弛豫后表面各层的电子特性进行了系统研究.发现四个台阶面的层间弛豫规律依次为-+-…,--+-…,--+-…和---+-…,与其平台-阶梯n(hkl)×(uvw)的表示法2(100)×(111),3(100)×(111),3(111)×(111)和4(111)×(111)中的原子排数n相关,即     

Single vibronic level fluorescence spectra of sulfur dioxide

Single vibronic level fluorescence spectra of sulfur dioxide have been recorded throughout most of the region corresponding to the $\text{A}\text{?}\text{-}\text{X}\text{?}$ absorption. These spectra show progressions in the symmetric stretching mode of at least five members. Twelve origins between 30 972 and 31 776 cm^?1 show remarkably similar Franck-Condon (FC) patterns for this progression. Seven origins between 31 840 and 32 257 cm^?1 show another distinct FC pattern. This behavior is repeated for three more regions of excitation, each with a different distinct FC pattern and each containing numerous origins spread throughout a region of about 700 cm^?1. The progressions in the symmetric bending mode are essentially absent in the lowest energy excitation spectra and then slowly increase in length as the excitation energy increases. There is limited activity in both even and odd quanta of the antisymmetric stretching mode. These results are interpreted in terms of the levels of a zero-order ¹B₁ electronic state (with zero-order origin at around 31 240 cm^?1) that are very strongly vibronically coupled to many more ¹A₂ levels (with lower energy zero-order origin). The bulk of the emission is what would be expected from the zero-order ¹B₁ levels spread among the ¹A₂ levels.     

Many-body effects in the (111)-silicon dangling-bond surface states

The many-body properties of the strongly correlated two-dimensional dangling bond electron gas of a (1 × 1)-Si surface have been analysed by means of an accurate solution of a Hubbard Hamiltonian. The experimental similarity between the (1 × 1) and the (7 × 7) faces allows us to extend our analysis to the latter surface. A peak appearing near the Fermi energy for the (7 × 7) face at low temperatures is related to a kind of “Kondo-peak” for the Hubbard Hamiltonian. Photoemission spectra for the (1 × 1) surface of highly doped Si can be understood in terms of our model.