Astrophysical S-factor of the d(p,γ)3He processby

We summarize the recent effective field theory (EFT) studies of low-energy electroweak reactions of astrophysical interest, relevant to big-bang nucleosynthesis. The zero energy astrophysical S(0) factor for the thermal proton radiative capture by deuteron is calculated with pionless EFT. The astrophysical S(0) factor is accurately determined to be S(0)=0.243 eV·b up to the leading order (LO). At zero energies, magnetic transition M₁ gives the dominant contribution. The M₁ amplitude is calculated up to the LO. A good, quantitative agreement between theoretical and experimental results is found for all observables. The demonstrations of cutoff independent calculation have also been presented.     

Correspondence between phenomenological and IBM-1 models of even isotopes of Yb

Energy levels and the reduced probability of E2–transitions for ytterbium isotopes with proton number Z=70 and neutron numbers between 100 and 106 have been calculated through phenomenological(Ph M)and interacting boson(IBM-1)models.The predicted low-lying levels(energies,spins and parities)and the reduced probability for E2–transitions results are reasonably consistent with the available experimental data.The predicted low-lying levels(gr–,β1–andγ1–band)produced in the Ph M are in good agreement with the experimental data compared with those by IBM-1 for all nuclei of interest.In addition,the phenomenological model was successful in predicting theβ2–,β3–,β4–,γ+2–and 1+–band while it was a failure with IBM-1.Also,the 3–band is predicted by the IBM-1 model for172Yb and174Yb nuclei.All calculations are compared with the available experimental data.     

First-principles study of structural,electronic and optical properties of orthorhombic SrZrO3

We have investigated the structural parameters, electronic structure and optical properties of orthorhombic SrZrO₃ using the plane-wave ultrasoft pseudopotential technique based on the first-principles density-functional theory (DFT). Our calculated structural parameters are in good agreement with the previous theoretical and experimental data. Band structure, density of states and chemical bonding have been systematically studied. Furthermore, the complex dielectric function, refractive index, extinction coefficient, optical reflectivity, absorption coefficient, loss function and optical conductivity are calculated, which show an optical anisotropy in the components of polarization directions (100), (010) and (001).     

First-principles study of structural, mechanical, electronic and optical properties of 3R- and 2H-CuGaO2

We calculated the structural parameters, elastic, mechanical, electronic and optical properties of 3R- and 2H-CuGaO₂ using the first-principles density-functional theory. The results show that the structural parameters of two phases are in good agreement with previous theoretical and experimental data. Two phases are mechanically stable, behave in ductile manner and have indirect band gap. The analyses of electronic structures and charge densities of two phases show mainly covalent nature in Cu-O bonds and coexistence of both ionic and covalent nature in Ga-O bonds. The optical properties are obtained and discussed, including the complex dielectric function, refractive index, extinction coefficient, optical reflectivity, absorption coefficient, energy-loss spectrum and complex conductivity function, which provide useful information for the future applications of CuGaO₂.     

高压下SiO_2的第一性原理计算

基于密度泛函理论(DFT)的第一性原理,采用Hartree-Fork(HF)方法,分别计算了Si O2的α-石英结构、金红石结构以及氯化钙结构的总能量随体积的变化关系。利用Murnaghan状态方程,通过能量和体积拟合,得到了3种结构的体变模量及其对压强的一阶导数。计算结果表明,随着压强的增加,Si O2会从α-石英结构转变为金红石结构,与实验结果和其它理论结果一致;金红石结构与氯化钙结构之间不存在相变,可以共存。此外,对具有α-石英结构的Si O2的晶格常数、电子态密度和带隙随压强的变化关系进行了计算和分析,结果表明:加压作用下,能带向高能方向移动,Si─O键缩短,电子数转移增加,带隙展宽,电荷发生重新分布。     

Calculation of prompt fission neutron spectra for 235U(n,f)

The prompt fission neutron spectra for the neutron-induced fission of ²³⁵U at E_n < 5 MeV are calculated using nuclear evaporation theory with a semi-empirical model, in which the nonconstant and constant temperatures related to the Fermi gas model are taken into account. The calculated prompt fission neutron spectra reproduce the experimental data well. For the n(thermal)+²³⁵U reaction, the average nuclear temperature of the fission fragment, and the probability distribution of the nuclear temperature, are discussed and compared with the Los Alamos model. The energy carried away by γ rays emitted from each fragment is also obtained and the results are in good agreement with the existing experimental data.     

0.5NdAlO3-0.5CaTiO3电子结构及光学性质的第一性原理计算

采用基于第一性原理密度泛函理论的平面波赝势方法,对0.5NdAlO₃-0.5CaTiO₃晶体进行结构优化,并对其能带结构,态密度和光学性质进行了理论计算.结构优化后晶格参数与实验数据相符合,误差小于1%;能带计算结果表明0.5NdAlO₃-0.5CaTiO₃为间接带隙,带隙值为0.52eV;费米面附近的能带由Nd-4f,O-2p,Nd-4p,Al-3p,Ti-4d层的电子态密度确定.同时也计算了该结构的介电函数,反射率和复折射率等光学性质.     

Structural,Electronic, and Optical Properties of Cubic Y<Subscript>2</Subscript>O<Subscript>3</Subscript>: First-Principles Calculations

Structural, electronic, and optical properties of cubic Y₂O₃ were studied using the plane-wave ultrasoft pseudopotential technique based on the first-principles density-functional theory (DFT). The ground-state properties were calculated and these results were in good agreement with the previous work. Furthermore, in order to understand the optical properties of cubic Y₂O₃, the complex dielectric function, refractive index, extinction coefficient, optical reflectivity, absorption coefficient, energy-loss function, and complex conductivity function were calculated, which were in favorable agreement with the theoretical and experimental values. We explained the origin of the absorption peaks using the theories of crystal-field and molecular-orbital bonding and investigated the relation between electronic structure and optical properties.     

ON THE ELECTRIC DIPOLE TRANSITIONS OF ψ(3770)

Various E1 transition rates for cc states are calculated in a QCD-motivated potential model.Relativistic corrections are found to be substantial.While a good agreement between theory and experiment is achieved for the rates of ψ(2s)→γχ_cJ and χ_cJ→γψ(1S)(J=0,1,2),the calculated rates for ψ(3770)→γχ_cJ are smaller by a factor of～2 than their experimental values obtained by the MarkⅢ collaboration.The effect of the 2³S₁—1³D1 mixing is possibly important and needed to be considered.     

First-principles study on the electronic and optical properties of BiFeO3

The structural, electronic, and optical properties of multiferroic bismuth ferrite (BiFeO₃) are investigated using density functional theory within generalized gradient approximation (GGA). The calculated lattice parameters are in good agreement with the experimental data. The electronic structure shows that BiFeO₃ has an indirect (very close to direct) band gap of 1.06 eV. The complex dielectric function, absorption spectra, refractive index, extinction coefficient, energy-loss spectrum and reflectivity are calculated, and the results are compared with the available experimental data. Finally, the optical properties of BiFeO₃ are discussed based on the band structure calculations.     

硝酸丙酯键离解能和热解机理的密度泛函理论研究

 采用B3LYP方法、在6-31G*基组水平上,优化了硝酸丙酯单体的平衡几何构型,计算了分子中各键的离解能。结果表明该分子中最弱的键为O—NO₂键,次弱键为C—O键。同时研究了热解机理,探索性的预测了断裂O—NO₂键及C—O键后的产物,并采用从头算法、半经验方法和密度泛函理论分别计算了硝酸丙酯的生成热,由半经验方法中的PM3得到的数值和实验结果符合较好。     

A Study for Nuclei 166Hf94—170Hf98 Using Cranking Shell Model with PNC Method

The properties of the band in even nuclei of ¹⁶⁶Hf₉₄—¹⁷⁰Hf₉₈ are investigated using cranking shell model with PNC method. The band crossing frequency, the interaction intensity between yrast and yrare bands, the aligned momentum, and the moment of inertia are calculated. The comparison between the calculation and experimental data shows a good agreement with each other if Lund systematic parameter is used for the Nilsson potential.     

First-principles studies of the electronic structure and optical properties of AgBO<Subscript>3</Subscript> (B=Nb,Ta) in the paraelectric phase

The electronic energy-band structure, density of states (DOS), and optical properties of AgBO₃ in the paraelectric cubic phase have been studied by using density functional theory within the local density approximation for exchange-correlation for the first time. The band structure shows a band gap of 1.533 eV (AgNbO₃)and 1.537 eV (AgTaO₃)at (M-⌈)point in the Brillouin zone. The optical spectra of AgBO₃ in the photon energy range up to 30 eV are investigated under the scissor approximation. The real and imaginary parts of the dielectric function and — thus the optical constants such as reflectivity, absorption coefficient, electron energy-loss function, refractive index, and extinction coefficient — are calculated. We have also made some comparisons with related experimental and theoretical data that is available.      

晶体PZCST:VO2+的EPR谱及光吸收谱的理论研究

采用双旋-轨耦合参量模型和3d¹电子组态在四角对称下的能级公式,计算了KZnClSO₄·3H₂O(PZCST): VO²⁺的EPR谱和光吸收谱,所得EPR谱和光吸收谱的理论结果与实验发现符合得很好. 研究发现,该晶体沿C₄轴局域对称结构呈压缩的四角畸变,其大小为0.47 nm;大的κ值表明VO²⁺的未配对电子的自旋极化对超精细结构常数有着较大的贡献.     

Ce:Co:LiNbO3晶体光折变性能研究

在LiNbO₃中掺进CeO₂和Co₃O₄,以Czchralski技术首次生长Ce:Co:LiNO₃, Ce:LiNbO₃, Co:LiNbO₃晶体.通过测试Ce:LiNbO₃, Co:LiNbO₃和Ce:Co:LiNbO₃晶体的指数增益系数, 位相共轭反射率和响应时间,计算晶体的有效载流子浓度和光电导.Ce离子能提高LiNbO₃晶体光折变灵敏度,Co离子能提高LiNbO₃晶体的响应速度和抗光致散射能力,从而Ce:Co:LiNbO₃晶体具有较高的指数增益系数,位相共轭反射率,响应速度.Ce:Co:LiNbO₃晶体具有优良的光折变性能.     

THE ENERGY DEPENDENCE OF THE CONDENSATION PROBABILITY IN THE COMPLEX PARTICLE EMISSION PROBABILITY

The condensation probability γ_β is studied by assuming that γ_β=γ_β(A, E)[ε_β/MeV]^χ When χ=0.425, the best agreement between the calculated dσ/dε and the experimental data is obtained for 18 reactions. For the same composite systems, the extracted γ_β(A, E) are nearly the same. When the mass of the composite system increases, the γ_β(A, E) increases too. For the α-decay nucleus ²¹⁰Po, γ_β(A, E) is larger than the others considerably.     

Constraint on the warped space from B→X_sγ

We analyze the theoretical prediction on the branching ratio of B→X_sγ to order Λ_EW²/Λ_KK² in extension of the standard model with a warped extra dimension and the custodial symmetry SU(3)_c×SU(2)_L×SU(2)_R×U(1)_X×P_LR, where Λ_KK denotes the energy scale of low-lying Kaluze-Klein excitations and Λ_EW denotes the electroweak energy scale. Contributions from the in nite series of Kaluze-Klein excitations are summed over through the residue theorem. The numerical result indicates that the present experimental data constrain the parameter space of the concerned model strongly.     

Structural, electronic and optical properties of orthorhombic distorted perovskite TbMnO3

This paper calculates the structural parameters, electronic and optical properties of orthorhombic distorted perovskite-type TbMnO3 by first principles using density functional theory within the generalised gradient approximation. The calculated equilibrium lattice constants are in a reasonable agreement with theoretical and experimental data. The energy band structure, density of states and partial density of states of elements are obtained. Band structures show that TbMnO3 is an indirect band gap between the O 2p states and Mn 3d states, and the band gap is of 0.48 eV agreeing with experimental result. Furthermore, the optical properties, including the dielectric function, absorption coefficient, optical reflectivity, refractive index and energy loss spectrum are calculated and analysed, showing that the TbMnO3 is a promising dielectric material.     

Design and Fabrication of Chirped Mirror

Chirped mirrors （CMs） are designed and manufactured. The optimized CM provides a group delay dispersion （ODD） of around -60fs^2 and average reflectivity of 99.4% with bandwidth 200 nm at a central wavelength of 800nm. The CM structure consists of 52 layers of alternating high refractive index Ta2O5 and low refractive index SiO2. Measurement results show that the control of CM manufacturing accuracy can meet our requirement through time control with ion beam sputtering. Because the ODD of CMs is highly sensitive to small discrepancies between the layer thickness of calculated design and those of the manufactured mirror, we analyze the error sources which result in thickness errors and refractive index inhomogeneities in film manufacture.