Ru2Si3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的密度泛函理论赝势平面波方法系统地计算了正交相Ru2Si3的电子结构、态密度和光学性质, 计算结果表明Ru2Si3是一种直接带隙半导体, 禁带宽度为0.51 eV; 其能态密度主要由Ru的4d层电子和Si的3p层电子的能态密度决定; 静态介电函数ε1（0）＝16.83; 折射率n0＝4.1025; 吸收系数最大峰值为2.8×105 cm-1; 并利用计算的能带结构和态密度分析了Ru2Si3材料的介电函数、反射谱、折射率以及消光系数等光学性质, 为Ru2Si3光电材料的设计与应用提供了理论依据.     

LaB6 电子结构及光学性质的第一性原理计算

采用基于密度泛函理论的第一性原理的分子动力学方法系统地计算了温度为313 K时laB₆基态的电子结构、态密度和光学性质. 能带结构分析表明laB₆ 属于导体, 其价带主要由B 的2p 态电子构成, 导带主要由La 的 5d, 6s 态电子构成, 静态介电常数ε₁(0)=213.7, 折射率n(0)=14.803, 吸收系数在可见光范围内最小波谷为21585 cm^?1; 并利用计算的能带结构和态密度分析了laB₆ 的介电函数实部和虚部以及由它们派生出来的光学常数, 即折射率、反射谱、吸收谱、光电导率和能量损失函数等; 其理论透光率的计算得出, 在紫外和近红外透光率几乎为零的情况下, 对可见光仍有很高的透光率, 呈“吊铃型”. 研究结果为laB₆ 在窗用隔热材料方面的应用提供了理论依据.     

First-principles studies of the adsorption of O2 on Al （001）

Oxidationisaubiquitousphenomenonofnature.Theeconomiclossduetooxidationisverylargeeveryyear.Theinvestigationoftheadsorptionofoxygenonthesur-facesofmetalsisofgreatimportanceforbetterunder-standingoftheoxidationmechanismbecauseitistheverybeginningstageofoxidationofmetals.Itisgenerallybe-lievedthattheprocessofO2adsorptiononmetalsisinanorderofO2?O?O-?O2-,andthefollowingstagesareoxidenucleation,growthandtheoxidefilmformation.Astheprocessofadsorptionistooquicktobeobservedbyexperiments,atheoreticals…     

Influence of deposition time on the morphology and optical properties of SiO<Subscript>2</Subscript>-ZnO composite photonic crystals

SiO2 photonic crystal were successfully prepared by vertical deposition and then used as a template to fabricate SiO2-ZnO composite photonic crystals on ITO substrates by electrodeposition and subsequent calcination. A number of different deposition times were used. The morphologies of the silica opals and SiO2-ZnO composite photonic crystals were investigated by scanning electron microscopy. It was found that ZnO particles grew randomly on the surfaces of the silica spheres when the deposition time was short. As the deposition time was increased, the ZnO particles grew evenly on the surfaces of the silica spheres so that the interstitial space of the silica template was filled with ZnO particles. Reflectance spectra of the SiO2-ZnO composite crystals revealed that all of the fabricated photonic crystals exhibit a photonic band gap in the normal direction.     

GaN/ZnO固溶体电子结构与光学性质的第一性原理研究

GaN/ZnO固溶体具有良好的光催化活性。为研究不同ZnO物质的量对GaN/ZnO固溶体能带结构和光吸收性能的影响,构建了一系列GaN/ZnO固溶体的随机原子结构模型。基于密度泛函理论计算不同ZnO物质的量对GaN/ZnO固溶体模型电子结构和光学性质的影响。研究结果表明： ZnO/GaN固溶体形成能与结合能均为负值,结构稳定。随着ZnO物质的量的增加,固溶体的带隙先呈现下降趋势,最后呈现小幅上升趋势。对于ZnO物质的量分数在13.89%至22.22%的GaN/ZnO固溶体,可以观察到光吸收峰强度在可见光区各个波长范围内均有较强吸收。通过研究不同ZnO物质的量对GaN/ZnO固溶体能带结构和光吸收性能的影响,为GaN/ZnO固溶体光催化材料的设计与制备提供了理论参考。     

高压下MgB2的电子结构的第一性原理计算

我们利用基于密度泛函理论框架下的广义梯度近似,结合全势(线性)缀加平面波方法,研究了高压下MgB2的电子结构,得到了几种压强下MgB2的电子能带结构.发现在Г点б带和π带随着压强的增大逐渐靠拢;体积的减小使价带带宽增大,而c/a的减小对这一变化没有贡献.     

闪锌矿型CdSe电子结构和光学性质的研究

采用基于密度泛函理论(DFT)框架下广义梯度近似平面波超软赝势法,计算了闪锌矿型CdSe的电子结构和光学性质。计算结果表明闪锌矿型CdSe为直接带隙半导体,禁带宽度为0.52eV。计算并分析了闪锌矿型CdSe的复介电函数、复折射率、反射率、吸收系数、损失函数和光电导率,计算得到其静态介电常数为6.18,折射率为2.49,吸收系数的最大峰值为298362.9cm1,理论计算结果与其他文献结果基本一致,为闪锌矿型CdSe的应用提供了理论参考数据。     

Electronic structures and nonlinear optical properties of XAuPH<Subscript>3</Subscript>

The studies on model systems XAuPH3(X-H,F,Cl,Br,I,CN,CH3)have been carried out by using ab intiol HF and DFT B3LYP methods at pseudopotential and double-zeta LANL2DZ level.The results are compared with those of MP2,The properties of the models.i.e.the atomic net charge populations.the frontier molecular orbitals and nonlinear optical(NLO)properties have been investigated under an applied electric field on the basis of optimized structures.The computational results show that for these models characterized as electron acceptor-metal-electron donor(A-M-D)system,the NLO properties are due to intramolecular charge-transfer interaction between the acceptor and the donor.The more charges transfer gives,the better NLO properties.In the selected model systems,IAuPH3 has the biggest βvec and γof 1184.1942 a.u.and 17341.9214 a.u.,whereas IC6H4PH3^ ,A TYPICAL a-π-D organic conjugated system,has βvec and γof 710.7697 and 11664.1405 a.u.respectively.In comparison.IAuPH3 has significant NLO properties.     

Fabrication and characteristics of intrinsic Josephson junctions in Bi<Subscript>2</Subscript>Sr<Subscript>2</Subscript>CaCu<Subscript>2</Subscript>O<Subscript>8+x</Subscript> single crystals

Mesa-structured intrinsic Jospehson junctions are fabricated in Bi2Sr2CaCu2O8 x single crystals.Typical current-voltage characteristics of intrinsic Josephson junctions are observed .which include multiple quasi-particle branches,surface junction with critical current lower than those of inner junctions.and subgap structures on quasi-particle branches,The corresponding physical explanations are also given .The energy gap voltage of the intrinsic Josephson junctions at 30 K is about 20mV Besides,The measured Ic-T relationship agrees quite well with the theoretical computations based on dx′-y′-wave superconductor.Our measured dI/dV-V relationship shows the V-shaped gap structure,obviously differing from the U-shaped gap structure of the s-wave superconductor.     

Preparation and radar-absorbing properties of Al<Subscript>2</Subscript>O<Subscript>3</Subscript>/TiO<Subscript>2</Subscript>/Fe<Subscript>2</Subscript>O<Subscript>3</Subscript>/Yb<Subscript>2</Subscript>O<Subscript>3</Subscript> composite powder

Al₂O₃/TiO₂/Fe₂O₃/Yb₂O₃ composite powder was synthesized via the sol-gel method. The structure, morphology, and radar-absorption properties of the composite powder were characterized by transmission electron microscopy, X-ray diffraction analysis and RF impedance analysis. The results show that two types of particles exist in the composite powder. One is irregular flakes (100-200 nm) and the other is spherical Al₂O₃ particles (smaller than 80 nm). Electromagnetic wave attenuation is mostly achieved by dielectric loss. The maximum value of the dissipation factor reaches 0.76 (at 15.68 GHz) in the frequency range of 2-18 GHz. The electromagnetic absorption of waves covers 2-18 GHz with the matching thicknesses of 1.5-4.5 mm. The absorption peak shifts to the lower-frequency area with increasing matching thickness. The effective absorption band covers the frequency range of 2.16-9.76 GHz, and the maximum absorption peak reaches -20.18 dB with a matching thickness of 3.5 mm at a frequency of 3.52 GHz.     

Nonlinear optical properties of Eu<Subscript>2</Subscript>O<Subscript>3</Subscript> doped 5ZnO-20Nb<Subscript>2</Subscript>O<Subscript>5</Subscript>-75TeO<Subscript>2</Subscript> glasses

The third-order optical nonlinearities, including third-order nonlinear susceptibility X^(3), nonlinear refractive index (n2) and temporal response, were measured with forward DFWM using Nd:YAG mode-locked pulse laser. The results show that Eu203 doped 5ZnO-20Nb2O5-75TeO2 glasses have large n2 and ultra-fast temporal response. Raman spectra show that Eu2O3 dopant induces the changes in the local structure of glasses. The higher the dopant concentration, the larger the nonlinear refractive n2 and the faster the temporal response. The enhancement on the third-order optical nonlinearities can be attributed to the deformation of the electronic clouds in [TeO4] enhanced by Eu2O3 dopant.     

Chemical quenching and inhibition of positronium in Cr<Subscript>2</Subscript>O<Subscript>3</Subscript>/Al<Subscript>2</Subscript>O<Subscript>3</Subscript> catalysts

The pore structure of Cr2O3/Al2O3 catalysts and the surface chemical properties of these pores were characterized by positron lifetime and coincidence Doppler broadening (CDB) measurements. Four lifetime components could be resolved from the positron lifetime spectrum, with two long lifetime components and two short lifetime components. The two long lifetimes τ4 and τ3 are attributed to ortho-positronium (o-Ps) annihilation in large pores and microvoids, respectively. With increasing Cr2O3 content, both τ4 and its intensity I4 show sharp decrease, while τ3 and its intensity I3 keep nearly unchanged. The Doppler broadening S parameters also show sharp decrease with increasing Cr2O3 content. Detailed analysis of the CDB spectrum reveals that the parapositronium (p-Ps) intensity also decreases with increasing Cr2O3 content. This indicates that the change of o-Ps lifetime τ4 is due to the chemical quenching by Cr2O3 but not spin-conversion of positronium. The decrease of o-Ps intensity I4 indicates that Cr2O3 also inhibits positronium formation.     

CdS_xSe_(1-x)合金结构、电子结构和光学性质的第一性原理研究

用密度泛函理论究了闪锌矿型三元合金体系Cd SxSe1-x的晶体结构、电子结构和光学性质.计算了组分参数在0≤x≤1范围内Cd SxSe1-x的电子结构、态密度和带隙,计算结果表明Cd SxSe1-x为直接带隙半导体材料,其带隙随Se含量的增加而减小.分析了Cd SxSe1-x的复介电函数和吸收系数等光学性质随光子能量变化的关系,随Se元素含量增加,各光学特性曲线向低能方向移动.     

Synthesis and Magnetic Properties of Spin-Liquid Tb2Ti2O7

Polycrystalline samples of a novel spin-liquid compound Tb2Ti2O7 were prepared by a standard solid-state reaction. X-ray diffraction at room temperature confirms that the synthesized compound of Tb2Ti2O7 is single phase with cubic unit cell constant a0 of 1.015 44 nm. Magnetic susceptibility measurements in the temperature range between 100 and 300 K give an effective moment of 9.44 μB and Curie-Weiss temperature of 12.68 K, respectively, indicating the dominance of antiferromagnetic interactions. However, below 50 K, the magnetic behavior of Tb2Ti2O7 deviates from Curie-Weiss law, whose origin remains suspicion.     

基于密度泛函理论的NiAs型MnTe第一原理计算

运用MaterialsStudio 6.0程序CASTEP软件包建立NiAs型MnTe单胞和1×1×10的超胞模型,采用GGA-PBE-TS近似,得出能带结构和态密度曲线。NiAs型MnTe为间接能隙窄带半导体,带隙为0.843eV;MnTe单胞的下价带在-12.5~-10.5eV,是一条二重简并带。在-6~-3.5eV和0.8~2.6eV主要由Mn原子的d态电子贡献,该Mn原子的d电子的有效质量较大,导致强的电子局域性;MnTe1×1×10超胞的帯隙为0.623eV,下价带位于-13~-11eV,对比单胞略微下移;在上价带和导带区域,MnTe超胞d态电子的能带和态密度都比MnTe单胞的变化平稳,整体形成较宽的赝能隙,说明Mn离子的共价性较强。     

CdS的电子结构和光学性质

根据密度泛函理论体系下的平面波赝势（PWP）和广义梯度近似（GGA）方法,利用第一性原理对CdS晶体闪锌矿结构进行研究计算,得到其平衡晶格常数、电子态密度分布、能带结构、光吸收系数等性质,详细讨论其电子结构,并且结合实验结果定性分析了半导体CdS的光学性质.     

EuPdGe3磁性与电子结构的第一性原理计算

为了探究EuPdGe3晶体材料的基态性质和磁晶易轴方向,本文采用基于密度泛函理论的VASP软件包计算研究了EuPdGe3材料的磁性与电子结构。计算结果表明EuPdGe3基态磁构型为A型反铁磁,磁晶易轴方向沿c轴方向。通过对EuPdGe3晶体的电子结构和实空间结构分析,得出了Ge2 4p电子态与Eu 4f电子态间的杂化是EuPdGe3晶体磁晶易轴方向沿c轴的原因。     

Electromagnetic modification of faceted-faceted Ni<Subscript>31</Subscript>Si<Subscript>12</Subscript>-Ni<Subscript>2</Subscript>Si eutectic alloy

In an electromagnetic field, the morphology of a binary faceted-faceted (FF) Ni31Si12-Ni2Si eutectic microstructure and the alloy’s mechanical properties were investigated. Hardness experiments demonstrated that the solidified ingots were significantly strengthened, and the hardness was improved to 63.1 and 786.6 on the Rockwell hardness C and Vickers hardness scales, respectively. Tests of friction and wear in stirred FF eutectic alloys showed excellent anti-fatigue and anti-adhesion wear performance. Alloy changed from an anomalous microstructure to a refined quasi-regular structure, and there was an increase in the lamellar microstructure fraction. The formation process of the refined quasi-regular microstructure and the resulting mechanical properties were investigated.     

Synthesis,Structure and Antitumor Activities of [Ni（dien）2][Ni（CN）4] Complex

Ni(II)-dien complex was prepared and characterized by X-ray diffraction. The crystal belongs to triclinic system, space group P-1, with crystallographic parametersa=0.888 13(18) nm,b=0.890 10(18) nm,c=1. 591 8(3) nm, α=77.71(3)°, β=89.12(3)°, γ=61.24(3)°,Z=2. The two dien molecules coordinate to the central Ni atom, the six nitrogen atoms form a distorted octahedron. Preliminary pharmacological tests showed this complex had antitumor activity against HepG₂ and HL-60 cell linesin vitro. Foundation item, Supported by the National Natural Science Foundation of China (29972034) Biography: Li Tao (1976-), male, Ph. D candidate, research direction: ophthalmology and chemicalbiology.     

Intense laser induced field ionization of C<Subscript>2</Subscript>H<Subscript>2</Subscript>, C<Subscript>2</Subscript>H<Subscript>4</Subscript>, and C<Subscript>2</Subscript>H<Subscript>6</Subscript>

Using HOMO Field Ionization Model, the tunneling probabilities and the theoretical threshold intensities of the field ionizations of acetylene, ethylene, and ethane in intense laser field are calculated. C2H2, C2H4, and C2H6 were irradiated by 800 nm, 100 fs laser pulses with the intensity range of 10^13-10^14 W/cm^2. A TOF-mass spectrometer was coupled to the laser system and used to experimentally investigate the field ionization of these molecules. The experimental ionization threshold intensities are obtained. The calculating results of the three molecules agree well with the experimental results, indicating that HOMO Field Ionization Model is valid for the ionization of polyatomic molecules in intense laser field.