Description of Chiral Doublet Bands in Odd-Odd Cs Isotopes

Properties of the chair doublet bands of the odd-odd Cs isotopes built on the π h_11/2 \otimes ν h_11/2 configuration are investigated systematicallywithin the supersymmetry scheme including many-body interactions andpossessing the SO(5)(or SU(5)) symmetry on the rotational symmetry.Quantitatively good results of the energy spectra, the energy staggering parameter as a function of the spin are obtained. The calculation shows that the stronger competition between the pairing and anti-pairing effects and the SU(3) symmetry broking more seriously exist in the stable chiral structure.     

喷雾热解法制备红色发光粉LiEu(SiO2)1/6W2O8的研究

采用喷雾热解法制备红色荧光粉LiEu(SiO₂)_1/6W₂O₈。研究了反应温度、前驱体溶液浓度、载气流速对实验结果的影响。通过扫描电镜、X射线衍射、激发和发射光谱对所制样品进行了研究,发现样品颗粒呈实心类球形、结晶度好、表面光滑、发光强度较高、粒径平均1.5μm左右且分布较窄。该类荧光粉激发主峰位于396nm,发射主峰位于615nm。LiEu(SiO₂)_1/6W₂O₈发光的色坐标为:x=0.667 9,y=0.3310,与NTSC的红色标准基本一致,该荧光粉色纯度非常高,适用于制造紫光芯片激发的白光LED。用喷雾热解法制备红色荧光粉LiEu(SiO₂)_1/6W₂O₈的研究尚未见报道。     

A Quenched Study for QCD Phase-Transition on Anisotropic Lattices

The QCD deconfinement phase transition in pure SU(3) gauge theory is studied on an anisotropic lattice. The critical temperature is determined to be T_c ≈ 285 MeV. The relation between the deconfinement phase transition and the breakdown of Z(3) center symmetry is also discussed.     

ZnMoO4∶Tb3+发光材料的制备与发光性能研究

采用燃烧法制备了ZnMoO₄∶Tb3+绿色荧光粉。XRD实验结果表明,样品在700 ℃基本形成单一的ZnMoO₄相,属三斜晶系,而Tb3+的掺入基本不影响ZnMoO₄的结构;TG-DTA研究结果表明,样品在680 ℃基本形成ZnMoO₄相;IR结果表明,在700 ℃燃烧后,没有出现其他有机物的峰,说明柠檬酸已完全分解,掺杂的少量Tb3+已完全溶入了ZnMoO₄的晶格中,形成ZnMoO₄∶Tb3+固溶体;SEM结果表明,700,750,800 ℃制备的样品随温度的提高颗粒的分散度逐渐提高;激发光谱的主要变化是随着ZnMoO₄∶Tb3+的生成而产生出主峰为488 nm处的强峰;发射光谱结果表明,随着ZnMoO₄∶Tb3+的形成,最佳激发波长488 nm下,出现了很强的544 nm处的发射峰,对应于Tb3+的5D₄→7F₅跃迁。通过ZnMoO₄中掺杂Tb3+,获得了一种有潜在应用价值的绿色荧光粉。     

Effective-field theory on the kinetic Ising model

As an analytical method, the effective-field theory (EFT) is used to study the dynamical response of the kinetic Ising model in the presence of a sinusoidal oscillating field. The effective-field equations of motion of the average magnetization are given for the square lattice (Z=4) and the simple cubic lattice (Z=6), respectively. The dynamic order parameter, the hysteresis loop area and the dynamic correlation are calculated. In the field amplitude h₀/ZJ-temperature T/ZJ plane, the phase boundary separating the dynamic ordered and the disordered phase has been drawn, and the dynamical tricritical point has been observed. We also make the compare results of EFT with that given by using the mean field theory (MFT).     

新化合物——Sr2CaMoO6的相变与晶体结构

本文用差热分析、X射线物相分析及点阵常数的精确测定等方法研究了新化合物Sr₂CaMoO₆的相变,证明该化合物在(767±5)℃存在一级位移型相变。低温相α-Sr₂CaMoO。属正交晶系,空间群为Pmm2,室温时点阵常数为:α=8.1933?,b=5.7611?,c=5.8410?。测量密度D_m=4.97g/cm³,单位晶胞内具有2个化学式量。高温相β-Sr₂CaMoO_关键词：     

Quantum orders in an exact soluble model

We find all the exact eigenstates and eigenvalues of a spin-1/2 model on square lattice: H=16g Sum S(y)(i)S(x)(i + empty set x)S(y)(i + empty set x + empty set y)S(x)(i + empty set y). We show that the ground states for g < 0 and g > 0 have different quantum orders described by Z2A and Z2B projective symmetry groups. The phase transition at g = 0 represents a new kind of phase transition that changes quantum orders but not symmetry. Both the Z2A and Z2B states contain Z2 lattice gauge theories at low energies. They have robust topologically degenerate ground states and gapless edge excitations.     

2-(4-氟代苯甲酰基)苯甲酸-铕配合物的合成、结构表征及荧光性能的研究

以硝酸铕、2-(4-氟代苯甲酰基)苯甲酸(HL)、1,10-菲咯啉(Phen)和三苯基氧膦(TPPO)合成了EuL₃(H₂O)₆,EuL₃Phen(H₂O)₄和EuL₃(TPPO)(H₂O)₅三种固态配合物。用元素分析、红外光谱、核磁共振氢谱对配合物进行了组分确定和结构表征。IR表明,2-(4-氟代苯甲酰基)苯甲酸与Eu3+形成配合物后,位于1 692 cm-1处羧基的ν_CO峰消失,2 500～3 200 cm-1处羧基的ν_O—H峰也消失,出现了羧酸盐特有的反对称伸缩振动吸收峰(ν_as(CO-₂))和对称伸缩振动吸收峰(ν_s(CO-₂)),且Δν(ν_as(CO-₂)-ν_s(CO-₂))与钠盐的Δν相近,说明羧酸根与Eu3+以对称双齿桥式配位。在1H NMR中,形成配合物后第一配体苯环上的质子峰变为宽峰且移向高场,Phen和TPPO中质子化学位移移向低场。室温下测定了配合物的荧光激发光谱和发射光谱,激发光谱表明配合物EuL₃(H₂O)₆,EuL₃Phen(H₂O)₄和EuL₃(TPPO)(H₂O)₅的最佳激发波长分别为353.0,355.0和357.0 nm;发射光谱均显示Eu3+离子的特征发射光谱,且表明Phen对Eu3+离子的荧光发射有明显增强作用。     

高压下γ'-Fe4N晶态合金的声子稳定性与磁性

利用基于密度泛函理论的第一性原理研究了高压下有序晶态γ’-Fe₄N合金的晶格动力学稳定性与磁性. 对比没有考虑磁性的γ’-Fe₄N的声子谱, 得出压力小于1 GPa时, 自发磁化诱导了铁磁相γ’-Fe₄N基态晶格动力学稳定. 压力在1.03-31.5 GPa时, Σ线上的点(0.37, 0.37, 0)、对称点X和M 上相继出现了声子谱软化现象. 压力在31.5-60.8 GPa时, 压致效应与自发磁化对诸原子的作用达到了稳定平衡, 表现出了声子谱稳定. 压力大于61.3 GPa时, 随着压力的增大压力诱导体系动力学不稳定性越强. 通过软模相变理论对于γ’-Fe₄N, 在10 GPa下的声学支声子的M点处软化现象的处理, 发现了动力学稳定的高压新相P2/m-Fe₄N. 压力小于1 GPa时高压新相P2/m-Fe₄N 是热力学稳定的相, 且磁矩与γ’-Fe₄N的磁矩几乎相同. 2.9-19 GPa时, P2/m相的焓比γ’相的焓小, 基态结构更稳定. 大于20 GPa时, 两相磁矩几乎相同.     

NMR study of coexistence of ferro- and antiferromagnetism in (Zr1−xNbx)Fe2

The magnetic phase diagram has been investigated in the C14 type (Zr_1−xNb_x)Fe₂ with x0.7 from ⁹³Nb NMR and magnetization measurements. In the compound with x = 0.825 a first order-like transition has been found to occur around 25 K from a canted state with the ferromagnetic moment in the basal plane to a ferromagnetic state with decreasing temperature.     

Elastic Collisions Between two Ground-State P and D Atoms at Low and Ultralow Temperatures

The PD（X^3∑^-） interaction potential is constructed using the CCSD（T） theory and the basis set, augcc-pV5Z. Using this potential, the spectroscopic parameters are accurately determined. The present Do, De, Re, ωe, ωeχe, αe, and Be are of 3.056 99 eV, 3.161 75 eV, 0.142 39 nm, 1701.558 cm^-1, 23.6583 cm^-1, 0.085 99 cm^-1, and 4.3963 cm^-1, respectively, which almost perfectly conform with the measurements. A total of 26 vibrational states is predicted when J = 0 by solving the radial Sehrodinger equation of nuclear motion. The complete vibrational levels, classical turning points, initial rotation and centrifugal distortion constants when J = 0 are reported for the first time, which favorably agree with the experiments. The total and various partial-wave cross sections are calculated for the elastic impact between two ground-state P and D atoms at 1.0 × 10^-12 - 1.0 × 10^-4 a.u. when they approach each other along the PD（X^3∑^-） potential. No shape resonances exist in the total elastic cross sections, though the peaks can be found for each partial wave until l=6. The shape of the total elastic cross sections is dominated by the s partial wave at very low temperatures. Due to the weakness of the shape resonances of each partial wave, they are all passed into oblivion by the strong total elastic cross sections.     

Tunneling Conductance in dx2-y2+idxy Mixed Wave Superconductor Graphene Junctions

Using the extended Blonder-Tinkham-Klapwijk formalism, we investigate the conductance spectra of normal metal/d_x²-y²+id_xy mixed wave superconductor graphene junctions. It is found that the conductance spectra vary strongly with the orientation of the gap and the amplitude ratio (Δ₁/Δ₀) of two components for d_x²-y²+id_xy mixed wave. The zero bias conductance isnearly 2 and the conductance peak vanishes in doped graphene forα=0 and Δ₁/Δ₀=1. The conductance increases with increasing the amplitude ratio of two components for α=π/4 and Δ₁/Δ₀=1. The ZBCP becomesobservable wide with 1F/Δ₀<100 for α=π/4 and Δ₁/Δ₀=1. This property is different from that in normal metal/d_x²-y² wave superconductor graphenejunctions.     

奇A核101Pd和101Ru的负宇称带能谱研究

将具有正宇称的gds组态空间扩大到包含具有负宇称的1h11/2轨道,采用修正的表面δ相互作用(MSDI)对101Pd和101Ru两个奇A核进行了形变HF计算,得到了基态和一些激发态的解.同时,还用近似角动量投影形变Hartree Fock(PDHF)方法对101Pd和101Ru进行了能谱计算,得到其正、负宇称带的解,计算结果与实验谱基本一致. Using modified delta interaction, enlarging the gds configuration space to include the 1h_11/2 orbital with negative parity, the deformed Hartree Fock calculations for both nuclei: 101Pd and 101Ru are performed. Their ground state and some excited configurations are obtained. The approximate angular momentum projected deform Hartree Fock (PDHF) method is also applied to nuclei 101Pd and 101Ru, and both of their positive and negative parity bands are obtained...     

Statistical Properties of Multispecies Competition Ecosystems Subjected to Dichotomous Noises

We investigate statistical properties of multispecies competition ecosystems subjected to both symmetric and asymmetric dichotomous noises. The expression of the stationary probability distribution function (SPDF) is analytically derived by means of mean-field approximation, and verified bystochastic simulations. The results indicate that: (i) A noiseamplitude (a₀), a noise autocorrelation time (τ₀) and a noise symmetry parameter (k) all can affect the SPDF; (ii) There is an optimal τ₀, which makes the mean value of population density be maximal, near which a transition takes place, i.e., the stationary mean value of species density (_st) suddenly falls to a lower constant; (iii) As k decreases, the maximum of< x>_st and the optimal τ₀ increase. The parameter planes of τ₀-a₀² and τ₀-k for the transition are plotted.     

Specific heat and anisotropic superconducting and normal-state magnetization of HoNi2B2C

The magnetization of single-crystal HoNi₂B₂C has been measured as a function of applied field (H) and temperature in order to probe the interplay between superconductivity and magnetism in this complex layered system. The normal-state magnetic susceptibility of HoNi₂B₂C is highly anisotropic with a Curie-Weiss-like temperature dependence for H applied perpendicular to the c-axis and with a much weaker temperature dependence for H applied parallel to the c-axis, indicating that the Ho⁺³ magnetic moments lie predominately in the tetragonal a−b plane below 20 K. High-field magnetization (2000 Oe), low-field magnetization (20 Oe) and zero-field specific heat all give an antiferromagnetic ordering temperature of T_N=5.0 K. Remarkably, in 20 Oe applied field both superconductivity (T_c=8.0 K) and antiferromagnetism (T_N=5.0 K) clearly make themselves manifest in the magnetization data. From these magnetization data a phase diagram in the H−T plane was constructed for both directions of applied field. This phase diagram shows a non-monotonic temperature dependence of H_c2 with a deep minimum at T_N=5 K. The high-field magnetization data for H applied perpendicular to the c-axis also reveal a cascade of three phase transitions for T < 5 K and H < 15 000 Oe, contributing to the rich H versus T phase diagram for HoNi₂B₂C at low temperatures.     

Nonequilibrium Phase Transition in Spin-S Ising Ferromagnet Driven by Propagating and Standing Magnetic Field Wave

The dynamical response of spin-S(S=1, 3/2, 2, 3) Ising ferromagnet to the plane propagating wave, standing magnetic field wave and uniformly oscillating field with constant frequency are studied separately in two dimensions by extensive Monte Carlo simulation. Depending upon the strength of the magnetic field and the value of the spin state of the Ising spin lattice two different dynamical phases are observed. For a fixed value of S and the amplitude of the propagating magnetic field wave the system undergoes a dynamical phase transition from propagating phase to pinned phase as the temperature of the system is cooled down. Similarly in case with standing magnetic wave the system undergoes dynamical phase transition from high temperature phase where spins oscillate coherently in alternate bands of half wavelength of the standing magnetic wave to the low temperature pinned or spin frozen phase. For a fixed value of the amplitude of magnetic field oscillation the transition temperature is observed to decrease to a limiting value as the value of spin S is increased. The time averaged magnetisation over a full cycle of the magnetic field oscillation plays the role of the dynamic order parameter. A comprehensive phase boundary is drawn in the plane of magnetic field amplitude and dynamic transition temperature. It is found that the phase boundary shrinks inwards for high value of spin state S.Also in the low temperature(and high field) region the phase boundaries are closely spaced.     

Soliton Lattice State of Spin—1／2 Antiferromagnetic Chain in an External Magnetic Field

One-dimensional spin-1-2 anisotropic Heisenberg antiferromagnet in a longitudinal external magnetic field is studied using bosonization method and Gaussian wave functional techniques which take account of the spatial structure.The magnetization and the energy of the ground state which depend on the external magnetic field are calculated.For the case of anisotropic parameter △＞△0,increasing of the external magnetic field above the threshold value leads to the appearance of the soliton lattice state in the ground state,until to an another critical field where the ground state changes to the canted state phase.Therefore,with increasing external magnetic field,the ground state experiences four different phases successively,namely,antiferromagnetic Ising,soliton lattice state canted state,and magnetization saturated phases.When △＜△0,the soliton lattice state phase does not appear,with increasing external field,the paramagnetic phase smoothly evolves into the canted state phase,finally reaches magnetization saturated phase.     

Ga含量对Mn2-xNiGa1+x结构和磁性的影响

系统研究了铁磁性形状记忆合金Mn_{2 -x}NiGa_1+x的结构、磁性和有序化转变. 研究表明: 随着Ga含量的增加, Mn_{2 -x}NiGa_1+x的母相结构由Hg₂CuTi 型逐渐转变到Cu₂MnAl型Heusler结构. 母相的晶格常数先增加后降低, 当x=0.3时达到最大值. 0.3 ≤x ≤0.8时, 材料除呈现Heusler结构的主相之外, 还出现了Ni₂In型六角相. 过渡金属中3d电子之间交换相互作用的减弱, 导致Mn_2-xNiGa_1+x主相的居里温度由Mn₂NiGa的590 K逐渐降低至Ga₂MnNi的220 K左右; 当x=0.6–0.8时, Ni₂In型六角相的居里温度与主相的居里温度出现分离. Ga对Mn的替代引起合金中原子间耦合作用的变化, 导致低温下Mn_{2 -x}NiGa_1+x的饱和磁化强度先增加后降低, 即x≤0.4时呈上升趋势, x>0.4时急剧下降. 差热分析结果显示, 随着x从0增加到1, 样品熔化温度逐渐降低, B2相到Heusler相的转变温度先降低后增加.     

Slab Percolation and Phase Transitions for the Ising Model

We prove, using the random-cluster model, a strict inequality between site percolation and magnetization in the region of phase transition for the d-dimensional Ising model, thus improving a result of [5]. We extend this result also at the case of two plane lattices (slabs) and give a characterization of phase transition in this case. The general case of N slabs, with N an arbitrary positive integer, is partially solved and it is used to show that this characterization holds in the case of three slabs with periodic boundary conditions. AMS classification: 60K35, 82B20, 82A25     

The order of magnetic phase transition in La(Fe1−xCox)11.4Si1.6 compounds

Magnetic transitions in La(Fe_1−xCo_x)_11.4Si_1.6 compounds with x=0–0.08, have been studied by DC magnetic measurements and Mössbauer spectroscopy. The temperature dependence of the Landau coefficients has been derived by fitting the magnetization, M(μ₀H), using the Landau expansion of the magnetic free energy. For x0.02 there is a strongly first-order magnetic phase transition between ferromagnetic and paramagnetic (F–P) states in zero external field and a metamagnetic transition from paramagnetic to ferromagnetic (P–F) above T_c. Increasing the cobalt content drives the F–P transition towards second order and eliminates the metamagnetic transition.