一类相空间中的准几率分布函数系

定义了一类相空间中的准几率分布函数系，这个准几率分布函数系直接建立在具有更加广泛意义的量子相空间Schr?dinger方程解的基础之上，其中定义_α=αp-i?q和_α=(1-α)q+i?p.发现了两个有趣的关系.(1)建立的量子相空间Schr?dinger方程的解实际上是对函数φ(λ)exp［i(1-α)qp］做窗口Fourier变换.(2)这个窗口函数g(λ)起着选择窗口形式的作用，而且不同的窗口对应着不同的分布函数.当g(λ)是一个代表Gauss窗的Gauss函数的时候，准几率分布函数就是一个类似于Husimi的分布函数f^HL_α(q,p)；当g(λ)是一个表示椭圆的复函数时，准几率分布函数就是一个椭圆分布函数f^E_α(q,p)；再在g(λ)为复函数的基础上附加α=0，就可得到标准序分布函数f^S(q,p)、反标准序分布函数f^AS(q,p)和Wigner分布函数f^W(q,p)，此时g(λ)表示高度为1/12π?而长度为λ的矩形窗. 关键词： 窗口Fourier变换 相空间 Wigner分布函数     

Change in work function during phase transition of Sc-O/W(1 0 0) system at high temperatures

The change in work function during the phase transition of a Sc-O/W(1 0 0) system at high temperatures of 1500-1700 K was investigated in order to elucidate the mechanism of the decrease in the work function of a (1 × 1)-Sc-O/W(1 0 0) surface. For the measurement of the work function using a secondary electron method at high temperatures, a sample holder was uniquely designed in order to suppress contributions of a large number of thermionic electrons emitted from a low-work-function surface. The obtained work function revealed that the change in work function strongly correlates with the coverage of Sc-O complexes, the stoichiometry of which is Sc₁O₁. The higher the coverage of ScO is, the lower the work function is, suggesting that the work function of the (1 × 1)-Sc-O/W(1 0 0) surface is reduced by the formation of ScO electric dipoles. Furthermore, the decrease in work function was modeled in combination with a previously reported kinetic model describing surface phenomena, i.e., the oxidation, oxygen desorption, diffusion and surface segregation of Sc-O complexes, during the phase transition of the Sc-O/W(1 0 0) surface at high temperatures. It was confirmed that the proposed model can explain the experimentally obtained change in work function very well. The value of the dipole moment of a ScO electric dipole was determined to be 2.7 × 10⁻³⁰ C m.     

利用FTIR研究彝药大红袍药物活性与光谱的关系

用傅里叶红外光谱法对彝药大红袍的药物活性与光谱的关系进行研究,通过分析,可知大红袍根皮的收敛止血作用与鞣质的2925.5、1035.2 cm-1等峰有关,顺气止痛与挥发油的1617.7cm-1等峰有关;根心的收敛止血作用与鞣质的2926.0、1048.9 cm-1等峰有关,顺气止痛与挥发油的1617.2、1732.3 cm-1等峰有关,且根皮的药物活性比根心好.这为彝药大红袍的快速鉴定、药理分析和质量监控提供科学依据.     

First-principles investigations of iridium low index surfaces

We report density functional theory (DFT) calculations for the surface energy, work function, and interlayer spacings for Ir(1 1 1), Ir(1 0 0), and Ir(1 1 0) surfaces using pseudopotential method and plane waves basis set. We investigate the convergence of the surface energy as a function of the number of layers in the slab for the Ir(1 0 0) surface. The results show that the surface energies calculated using the bulk total energies obtained by a fit to a series of slab total energies converge within 0.01 J/m². We also investigate the convergence of the work function and interlayer spacings as a function of the number of layers in the slab, for the Ir(1 0 0) surface. Employing the local-density approximation (LDA) and the generalized gradient approximation (GGA) for the exchange correlation functional, we obtained a very good agreement of the calculated surface energies and work functions with experimental results. For the studied surfaces, the calculations give interlayer relaxations that are in an excellent agreement with available low-energy electron diffraction (LEED) analysis. Furthermore, we discuss the performance of the LDA and GGA for the exchange correlation functional in describing the various surface properties. The results show that calculations using GGA give results that are in a better agreement with experiment than the LDA.     

Exact maximal height distribution of fluctuating interfaces

We present an exact solution for the distribution P(h(m),L) of the maximal height h(m) (measured with respect to the average spatial height) in the steady state of a fluctuating Edwards-Wilkinson interface in a one dimensional system of size L with both periodic and free boundary conditions. For the periodic case, we show that P(h(m),L)=L(-1/2)f(h(m)L(-1/2)) for all L>0, where the function f(x) is the Airy distribution function that describes the probability density of the area under a Brownian excursion over a unit interval. For the free boundary case, the same scaling holds, but the scaling function is different from that of the periodic case. Numerical simulations are in excellent agreement with our analytical results. Our results provide an exactly solvable case for the distribution of extremum of a set of strongly correlated random variables.     

钛酸铅及掺杂体系纳米晶A_1对称性横光学声子模的特征

本文讨论了ＰｂＴｉＯ３、Ｐｂ１－ｘＬａｘＴｉ１－ｘ／４Ｏ３和Ｐｂ１－ｘＣａｘＴｉＯ３纳米晶拉曼散射中Ａ１（ＴＯ）声子峰的不规则线型和多峰劈裂现象。认为以简正振动坐标构成的非谐性双势阱势能函数和Ｍｏｒｓｅ势能函数的Ｓｃｈｒｄｉｎｇｅｒ方程的解与实验观测到的Ａ１（１ＴＯ）模式在高温下的劈裂峰特征比较一致。从能量角度解释了随ｃ／ａ下降,ωＡ１（ＴＯ）快速向低频移动的原因。     

Variable Separation Solutions in (1+1)-Dimensional and (3+1)-Dimensional Systems via Entangled Mapping Approach

In this paper, the entangled mapping approach (EMA) is applied to obtain variable separation solutions of (1 1)-dimensional and (3 1)-dimensional systems. By analysis, we firstly find that there also exists a common formula to describe suitable physical fields or potentials for these (1 1)-dimensional models such as coupled integrable dispersionless (CID) and shallow water wave equations. Moreover, we find that the variable separation solution of the (3 1)-dimensional Burgers system satisfies the completely same form as the universal quantity U1 in (2 1 )-dimensional systems. The only difference is that the function q is a solution of a constraint equation and p is an arbitrary function of three independent variables.     

Calculation of linear and nonlinear optical absorption coefficients of a spherical quantum dot with parabolic potential

In the effective mass approximation, we calculated the binding energy and wave function for the 1s-, 1p-, 1d- and 1f-states of a spherical quantum dot (QD) with parabolic potential by using a combination of quantum genetic algorithm (QGA) and Hartree-Fock-Roothaan (HFR) method. In addition, we also investigated the linear and the third-order nonlinear optical absorption coefficients as a function of the incident photon energy for the 1s-1p, 1p-1d and 1d-1f transitions. Our results are shown that the existence of impurity has great influence on optical absorption coefficients. Moreover, the optical absorption coefficients are strongly affected by the incident optical intensity, relaxation time, parabolic potential and dot radius.     

Superscaling of percolation on rectangular domains

For percolation on (RL)xL two-dimensional rectangular domains with a width L and aspect ratio R, we propose that the existence probability of the percolating cluster E(p)(L,epsilon,R) as a function of L, R, and deviation from the critical point epsilon can be expressed as F(epsilonL(y(t))R(a)), where y(t) identical with1/nu is the thermal scaling power, a is a new exponent, and F is a scaling function. We use Monte Carlo simulation of bond percolation on square lattices to test our proposal and find that it is well satisfied with a=0.14(1) for R>2. We also propose superscaling for other critical quantities.     

Spectral functions in the two-dimensional Hubbard model within a spin-charge rotating frame approach

We have performed electronic spectral function calculations for the Hubbard model on the square lattice using recently developed quantum SU(2) × U(1) rotor approach that enables a self-consistent treatment of the antiferromagnetic state. The collective variables for charge and spin are isolated in the form of the space-time fluctuating U(1) phase field and rotating spin quantization axis governed by the SU(2) symmetry, respectively. As a result interacting electrons appear as composite objects consisting of bare fermions with attached U(1) and SU(2) gauge fields. This allows us to write the fermion Green’s function in the space-time domain as a product of the SU(2) gauge fields, U(1) phase propagator and the pseudo-fermion correlation function. Consequently, the calculation of the spectral line shapes now reduces to performing the convolution of spin, charge and pseudo-fermion Green’s functions. The collective spin and charge fluctuations are governed by the effective actions that are derived from the Hubbard model for any value of the Coulomb interaction. The emergence of a sharp peak in the electron spectral function in the antiferromagnetic state indicates the decay of the electron into separate spin and charge carrying particle excitations.     

(1 + 2)-Dimensional sub-strongly nonlocal spatial optical solitons: Perturbation method

By extending the (1 + 1)-dimensional [(1 + 1)-D] perturbation method suggested by Ouyang et al. [S. Ouyang, Q. Guo, W. Hu, Phys. Rev. E. 74 (2006) 036622] to the (1 + 2)-D case, we obtain a fundamental soliton solution to the (1 + 2)-D nonlocal nonlinear Schrödinger equation (NNLSE) with a Gaussian-type response function for the sub-strongly nonlocal case. Numerical simulations show that the soliton solution obtained in this paper can describe the soliton states in both the sub-strongly nonlocal case and the strongly nonlocal case. It is found that the phase constant and the power of the (1 + 2)-D strongly nonlocal spatial optical soliton with a Gaussian-type response function are both in inverse proportion to the 4th power of its beam width.     

Relative magnitudes of the J/ψ and ψ′ wave functions at the origin

We probe that in the approximation of a non-relativistic quarck-antiquark model the 2S wave function at the origin is smaller (larger) than the 1S wave function if the binding potential is a concave (convex) function of the interparticle distance.     

Electron cotunneling transport in gold nanocrystal arrays

We describe current-voltage (I-V) characteristics of alkyl-ligated gold nanocrystals ~5 nm arrays in a long screening length limit. Arrays with different alkyl ligand lengths have been prepared to tune the electronic tunnel coupling between the nanocrystals. For long ligands, electronic diffusion occurs through sequential tunneling and follows activated laws, as a function of temperature σ∝e(-T(0)/T) and as a function of electric field I∝e(-E(0)/E). For better conducting arrays, i.e., with small ligands, the transport properties cross over to the cotunneling regime and follow Efros-Shklovskii laws as a function of temperature σ∝e(-(T(ES)/T)(1/2) and as a function of electric field I∝e(-(E)(ES)/E)(1/2). The data show that electronic transport in nanocrystal arrays can be tuned from the sequential tunneling to the cotunneling regime by increasing the tunnel barrier transparency.     

The co-induced 1 × 2 ↔ 1 × 1 phase transition of Pt(110) studied by leed and work function measurements

The adsorption of CO on the reconstructed 1 × 2-Pt(110) surface causes a lifting of the reconstruction which has been studied by LEED and work function measurements. The work function initially decreases until at γ = 0.2 the lifting of the reconstruction begins. A comparison with Pt(100) and Pt(111) shows that the similar behaviour of CO-induced work function changes on all three low-index planes of Pt appears to be related with a similar binding geometry of CO adsorbed on top of a (quasi-)hexagonal configuration of Pt atoms. No hysteresis is observed in the adsorption/desorption equilibrium of CO on Pt(110). Although the energetics of the CO-induced phase transition on Pt(110) appear to be analogous to those of the phase transition 1 × 1 ⇹ hex of Pt(100), a number of differences exist between the two surfaces which can be explained by the different structural properties of the various surface phases involved.     

第一性原理研究Al-Cu-Li合金中T1相的腐蚀机理

利用密度泛函理论的第一性原理,讨论Al-Cu-Li合金中主要析出相T1相(Al6Cu4Li3)的表面性质,计算不同终结面的表面能和表面电子功函数,并探讨应力作用和常见合金元素对Al/T1界面的影响.结果表明:T1相的表面能与表面的原子排列有关,不同的表面通过应变释放重构,进而获得不同的表面能.表面电子功函数则与表面原子种类有关,由于Li的电负性最小,含Li原子的表面通常有较低的电子功函数,进而降低材料的耐蚀性.此外,在应力作用下,T1相一些表面的电子功函数变化与纯金属是相反的.压应力下T1相电子功函数降低,材料更加容易被腐蚀;张应力下T1相功函数增加,材料更加耐腐蚀.同时,通过计算Al/T1界面中Ag,Zn和Mg 3种合金元素的替位能,可以发现,这3种元素都有利于降低界面能,且Ag的作用最明显.     

(3+1)维 KdV 方程新的精确解和孤子解

用普通Korteweg-de Vries(KdV)方程作变换,构造(3 1)维KdV方程的解,获得了新的孤子解、Jaoobi椭圆函数解、三角函数解和Weierstrass椭圆函数解.     

Fractional-order desorption of D2 from a Pd(110) surface

The desorption of deuterium from the low temperature (α₂) state on a Pd(110) surface was studied by TDS, LEED and Δφ. Simultaneous measurements of the isothermal desorption of the α₂ state, intensity of a half-order beam of the (1 × 2) phase and work function change show clearly that the desorption of this low temperature state is associated with the phase transition (1 × 2) to (2 × 1). This transition correlation with a work function change of ∼ 70 mV. The desorption follows nearly zero-order kinetics with an activation energy of ∼ 71 kJ mol⁻¹. The desorption kinetics are thus closely analogous to those on Ni(110).     

Influence of “ytterbium nanofilm–silicon Si(111)” interfaces on the valence of ytterbium

The work function of ytterbium films of nanometer thickness (from 1 to 16 monolayers) has been measured. The films have been prepared by sputtering of ytterbium in an ultrahigh vacuum on n- and p-type Si(111)7 × 7 silicon substrates with an electrical resistivity from 1 to 20 Ω cm. It has been shown that, in the films with a thickness of less than 8 monolayers, the work function depends nonmonotonically on the amount of ytterbium deposited on the surface (Friedel oscillations), whereas in the films with a thickness of more than 8 monolayers, the work function takes on a constant value (3.3 eV) that exceeds the work function for macroscopic samples (2.6 eV). This difference is associated with the fact that, during the formation of an Yb–Si interface, the large difference in the work functions of ytterbium and silicon (4.63 eV) leads to the transfer of a significant fraction of electrons from the metal to the semiconductor. This transfer of electrons from the film to silicon is accompanied by the lowering of the Yb 5d level below the Fermi level. As a result, the valence of the metal and, accordingly, the work function increase.     

Adsorption structure and work function of dicarboxylic acid on Cu(1 1 0) surface

We investigated the relation between work function and the adsorption structure of dicarboxylic acids (organic molecules) such as succinic acid (HOOC-CH₂-CH₂-COOH) and an adipic acid (HOOC-(CH₂)₄-COOH) on a Cu(1 1 0) surface (electrode) as a function of the surface temperature using a Kelvin probe (KP). The work function changes of the two acids are similar. The work function increases by adsorption at room temperature due to ionization of molecules and then decreases with increasing temperature until 450 K due to the effects of change in the dipole moment of the conformational change of the molecule. From 450 to 600 K, the work function is constant because of competition between desorption and change in the dipole moment of molecules. It then reached the clean-surface value. Experiments clarified that the work function was affected by the adsorbed difference in conformation of molecules.     

Critical behaviors of a (2 + 1)-dimensional black hole with a nonlinear electrodynamics source

On the basis of a charged BTZ black hole, we add an extra term in the metric function to describe the contribution from nonlinear electrodynamics. In this way we artificially construct a (2 + 1)-dimensional black hole in general relativity coupled with a nonlinear electrodynamics source. The thermodynamic quantities and Smarr formula are derived. It is found that this black hole has T−S criticality like that of an RN-AdS black hole. Further modifying the metric function, we obtain a (2 + 1)-dimensional black hole possessing P−V critical behaviors similar to that of van der Waals fluid. To our knowledge, this is the first example of (2 + 1)-dimensional black holes having this kind of critical behavior.