液晶空间光调制器相位调制的色散特性研究

提出用椭偏仪法测试了自制液晶空间光调制器(LCSLM)的相位调制色散特性.椭偏仪法具有光路简单,结果准确,测试自动化等优点,相比单色光源干涉仪测量方法更加简单实用.结果表明,在短波长(450 nm)处,LCSLM的相位调制能力为1.54λ(λ=450 nm),在长波长(800 nm)处,LCSLM的相位调制能力为0.70λ(λ=800 nm),与理论分析的色散特性基本一致.     

Vibrational Dynamics and Heat Capacity of Poly(3-methylthiophene): A Conducting Polymer

Using the Urey–Bradley force field and Wilson's GF matrix method as modified by Higgs, normal modes of vibration and their dispersions in poly(3-methylthiophene) have been obtained. They provide a detailed interpretation of its I.R. and Raman spectra. Characteristic features of the dispersion curves, such as regions of high density-of-states, repulsion, and character mixing of dispersive modes, are discussed. Predictive values of the heat capacity as a function of temperature have been calculated.     

Effect of change in structural and magnetic states of Pt<Subscript>74.1</Subscript>Fe<Subscript>25.9</Subscript> alloy on its optical properties

The effect of atomic disordering on the optical properties of Pt_74.1Fe_25.9 alloy, whose stoichiometry is close to that of Pt₃Fe, has been investigated. The optical constants of ordered and plastically deformed alloys, which are, respectively, in the paramagnetic and ferromagnetic states, have been measured by the polarimetric method. The frequency dispersions of the permittivity, optical conductivity, and reflectivity, as well as the microscopic characteristics of conduction electrons (plasma and relaxation frequencies), have been calculated. The energy dependences of the optical conductivity are compared to the calculated energy-band structure of atomically ordered and disordered Pt₃Fe compounds.     

AB INITIO STUDY ON THE ELECTRONIC STRUCTURE AND MAGNETISM OF MnAs, MnSb, AND MnBi

We report the results of first-principles calculations on the electronic structure in ferromagnetic and non-magnetic hexagonal MnV (V=As, Sb, Bi). The calculations are based on the local-spin-density approximation (LSDA) of the density-functional theory (DFT) as well as the atomic sphere approximation (ASA) in the linear muffin-tin orbitals (LMTO) method. For the non-spin-polarized case, the calculated bands in these compounds exhibit p-d mixing in the vicnity of Fermi energy and the Mn 3d bands dominate the antibonding parts of p-d hybride. The spin-polarization in ferromagnetic states are mainly due to the splitting of anti-bonding bands from p-d mixing. The calculated spin moments in these compounds agree fairly well with experimental values and refine previous band calculations. In the spin-polarized band structure, the Mn 3d electrons are found to exhibit week dispersions.     

Electronic band structure of Cu3Au: An angle-resolved photoemission study along the [111]-direction

High-resolution normal photoemission (ARPE) spectra have been recorded for Cu₃Au(111) with the use of polarized synchrotron and rare-gas resonance radiation in the photon energy range from 9 to 27 eV. It is for the first time that dispersions of the gold-like bands have been found experimentally. Using a fully relativistic layer-KKR photoemission formalism, occupied and unoccupied bands as well as one-step-model photoemission spectra have been calculated. The comparison of calculated spectra with experimental ones and the observation of direct-transition resonances upon photon energy near the Brillouin zone-center reveal a shift of the unoccupied ground-state bands by about +2.5 eV (self-energy shift). The direct-transition structures in the experimental spectra have been exploited to determine the dispersions of the occupied bands along the [111] direction (A line in k space). In order to determine the wave vector of the experimental direct transitions we used as final state that calculated unoccupied band along [111], which also exists in pure copper and gold up to about 20 eV above the Fermi energy (“unfolded” band structure), shifted by + 2.5 eV. The experimental occupied bands with Cu character are in very good agreement with theory after shifting the latter by about 0.3 eV to lower energy, whereas somewhat bigger discrepancies exist for the gold-like bands.     

Non-collinear magnetisation of V clusters supported on a Cu (1 1 1) surface: Theory

Magnetic properties and electronic structure of V clusters supported on a Cu (1 1 1) substrate, have been calculated from a first principles method. We observe in general non-collinear magnetic structures that are the result of antiferromagnetic interactions on a frustrated lattice. The values of the magnetic moments range from ∼0 to 2.7 μ_B/atom, depending on cluster geometry.     

Direct numerical simulations of electrophoresis of charged colloids

We propose a numerical method to simulate electrohydrodynamic phenomena in charged colloidal dispersions. This method enables us to compute the time evolutions of colloidal particles, ions, and host fluids simultaneously by solving Newton, advection-diffusion, and Navier-Stokes equations so that the electrohydrodynamic couplings can be fully taken into account. The electrophoretic mobilities of charged spherical particles are calculated in several situations. The comparisons with approximation theories show quantitative agreements for dilute dispersions without any empirical parameters; however, our simulation predicts notable deviations in the case of dense dispersions.     

"双"吡唑啉类化合物的荧光光谱理论研究

采用量子化学半经验方法RHF／AM1,RHF／PM3对4种“双”吡唑啉衍生物进行构型优化,经振动分析未出现虚频率,在此基础上用RHF／CIS方法分别计算了它们的荧光光谱,所得结果与文献值基本符合。     

Cohesivity and Colloidal Properties Affecting the Dispersibility of Ni/Sb-Doped TiO2 Powders

The colloidal properties and cohesivity of Ni/SB-doped TiO₂ powders (normal sizes ranging from 0.7–1.3 (μm) have been studied. Pretreatment of the powders via washing proved to be necessary in order to obtain consistent and reproducible aqueous suspension behavior. The point-of-zero-charge of the powders was found to range from pH 5.8-7.8 from measurements of the sedimentation volume and particle size analyses performed for dispersions prepared at various pH values. Surface and mass titration studies corroborated these results. Stability characterization studied in nonaqueous solvents revealed the partial solubility parameters for the powders as well as the usefulness of drying the powder for the preparation of stable nonaqueous dispersions. In addition, tensile strength measurements revealed that drying the powders reduces their cohesivity. These results are useful for determining favorable processing strategies and optimal conditions for dispersibility in coatings formulations.     

Direct determination of free energies of colloidal dispersions

Helmholtz free energies of electrostatically-stabilized colloidal dispersions of monodispersed spherical particles have been obtained using computer experiments. Boltzmann sampling has been shown to be sufficient for determining free energy differences between two dispersions whose pair-potentials are close to each other. Non-Boltzmann sampling has been used when the pair-potentials differ substantially. These results have been compared with the results based on perturbation theory. The techniques used, thus, offer a direct method to test the latter.     

On the adhesion theory of solids in terms of the dielectric formalism

The calculated dependences for computing the energy and strength of the ideal adhesion for solids (metals, semiconductors, and dielectrics) have been obtained in terms of the dielectric formalism. The inclusion of the linear and quadratic dispersions of surface plasmons provides a good agreement of the calculated values with the available data.     

HF(X1Σ+)的光谱跃迁精细结构的Dunham方法研究

用从头计算法QCISD/6-311++G**得到了HF(X1Σ+)的势能曲线,基于Dunham方法得到了HF(X1Σ+)的光谱常数,从而得到了(3→1,2→0)的泛频跃迁精细结构,计算值与实验值吻合较好。用几种不同的方法计算了HF(X1Σ+)的各阶力常数,其计算结果比较一致。     

Energy bands of atomic monolayers of various materials: Possibility of energy gap engineering

The mobility of graphene is very high because the quantum Hall effects can be observed even at room temperature. Graphene has the potential of the material for novel devices because of this high mobility. But the energy gap of graphene is zero, so graphene cannot be applied to semiconductor devices such as transistors, LEDs, etc. In order to control the energy gaps, we propose atomic monolayers which consist of various materials besides carbon atoms.To examine the energy dispersions of atomic monolayers of various materials, we calculated the electronic states of these atomic monolayers using density functional theory with structural optimizations. The quantum chemical calculation software Gaussian 03 was used under periodic boundary conditions. The calculation method is LSDA/6-311G(d,p), B3LYP/6-31G(d), or B3LYP/6-311G(d,p).The calculated materials are C (graphene), Si (silicene), Ge, SiC, GeC, GeSi, BN, BP, BAs, AlP, AlAs, GaP, and GaAs. These atomic monolayers can exist in the flat honeycomb shapes. The energy gaps of these atomic monolayers take various values. Ge is a semimetal; AlP, AlAs, GaP, and GaAs are indirect semiconductors; and others are direct semiconductors.We also calculated the change of energy dispersions accompanied by the substitution of the atoms. Our results suggest that the substitution of impurity atoms for monolayer materials can control the energy gaps of the atomic monolayers.We conclude that atomic monolayers of various materials have the potential for novel devices.     

Surface electronic structure of Ge(001)2 × 1: experiment and theory

Detailed studies of the surface electronic structure of Ge(001)2 × 1 have been performed with angle-resolved photoemission. Five surface structures are identified in the spectra and their initial-energy dispersions E(k_∥) are presented along the [010] direction. Employing the local density approximation and Green's functions, the surface band structure along this direction has been calculated self-consistently for an asymmetric dimer model of the 2 × 1-reconstructed surface. Four of the five experimental surface structures are identified with calculated surface states or resonances, i.e. the dangling-bond state and two different back-bond resonances. Excellent agreement is obtained between the experimental and theoretical dispersions for these surface electronic bands.     

Band offsets engineering at Cd_xZn_(1-x)S/Cu_2ZnSnS_4 heterointerface

Cd_xZn_(1-x)S/Cu_2ZnSnS_4 (CZTS)-based thin film solar cells usually use Cd S as a buffer layer, but due to its smaller band gap(2.4 e V), Cd S film has been replaced with higher band gap materials. The cadmium zinc sulfide(Cd Zn S) ternary compound has a higher band gap than other compounds, which leads to a decrease in window absorption loss. In this paper, the band offsets at Cd_xZn_(1-x)S/Cu_2ZnSnS_4 (CZTS) heterointerface are calculated by the first-principles, densityfunctional and pseudopotential method. The band offsets at Cd_(1-x)Zn_x S/CZTS heterointerface are tuned by controlling the composition of Zn in Cd_(1-x)Zn_x S alloy, the calculated valence band offsets are small, which is consistent with the commonanion rule. The favorable heterointerface of type-I with a moderate barrier height( 0.3 e V) can be obtained by controlling the composition of Zn in Cd_(1-x)Zn_x S alloy between 0.25 and 0.375.     

Effective charges and radial integrals in A = 17 nuclei

Radial integrals involving single-particle states in ¹⁷O have been determined from sub-Coulomb heavy-ion transfer reactions. Corresponding integrals in ¹⁷F have been inferred. Neutron and proton effective charges have been calculated. It is suggested that radial matrix elements obtained by the present technique be used as a consistent method for extracting effective charges from experimental data, and as starting points for microscopic calculations of effective charges.     

Vibrational Dynamics of Poly(l-asparagine)

The normal modes and their dispersions for poly(l-asparagine) (PLN) in the α-helical form have been obtained in a reduced zone scheme with Wilson's GF matrix method as modified by Higgs. The results indicate that the modes below 1350 cm^?1 show appreciable dispersion. Optically active frequencies corresponding to the zone center and zone boundary are identified and discussed. Some of the characteristic features of the dispersion curves are repulsion accompanied by an exchange of character and von Hove singularities. Amide modes, side chain modes, and mixed modes are reported. The heat capacity calculated from the dispersion curves via density-of-states using Debye's relation is compared with the experimental data in the temperature range of 220–390 K.     

CsMgX3：V^2＋（X=Cl,Br）中配体SO耦合对EPR参量的贡献

用双自旋－轨道耦合系数模型研究了晶体ＣｓＭｇＣｌ３和ＣｓＭｇＢｒ３中掺杂Ｖ２＋离子的ＥＰＲｇ因子和零场分裂Ｄ。计算中，用半经验方法确定了分子轨道系数。研究表明，对Ｂｒ－这类有强共价性和大ＳＯ耦合系数的配体，其ＳＯ耦合作用对络合物ＥＰＲ参量的贡献不可忽略。     

含铅空位PbWO4晶体光学性质的模拟计算

为了研究钨酸铅晶体中铅空位对光学性质的影响,利用完全势缀加平面波局域密度泛函近似,按照能量最低原理采用共轭梯度方法,对含铅空位的PbWO4(PWO)晶体进行结构优化处理。计算了含铅空位的PWO晶体的电子结构、复数折射率、介电函数及吸收光谱,并与完整的PWO晶体进行了比较。结果表明：完整的PWO晶体在可见和近紫外区域内无吸收,而含铅空位的PWO晶体在可见和近紫外区域出现2个明显的吸收峰,这2个吸收峰可分解成4个高斯线型的吸收带,它们的峰值分别为350nm、405nm、550nm和670nm。可以得出这样的推论：PWO晶体中350nm、420nm、550nm和670nm吸收带的出现都与铅空位的存在有关。