立方结构Fe基磁性材料弹性系数第一性原理计算

通过赝势平面波法(CASTEP)及全电势线性缀加平面波法(FLAPW)，以bcc-Fe为对象，研究第一性原理计算立方结构Fe基磁性材料弹性系数的方法，分析影响计算立方结构Fe基磁性材料弹性系数准确度的各项因素. 结果表明，在第一性原理弹性系数计算中，晶格常数是决定弹性系数计算准确度的关键因素；势函数的选择也会影响计算准确度. 使用全电势基矢的FLAPW法可以得到更为精准的弹性系数计算结果. 计算得到bcc-Fe的弹性系数C₁₁，C₁₂，C₄₄分别为246 GPa，121 GPa，113 GPa，与实验值基本一致. 利用本方法，计算了新型Fe-Ga磁致伸缩材料的弹性系数C₁₁，C₁₂，C₄₄分别为207 GPa，166 GPa及108 GPa. 关键词： 弹性系数 磁致伸缩材料 赝势平面波法 全电势线性缀加平面波法     

纳米X1-Y2SiO5: Eu3+发光光谱的理论研究

从晶体结构参数和Eu³⁺离子等的物性参数出发，用Faucher的静电模型，计及远程环境影响，且用自洽求解方法确定配位离子的诱导电偶极矩，系统地计算了纳米晶X₁-Y₂SiO₅: Eu³⁺的晶场参数，并延伸此模型用于跃迁强度计算．给出了在C₁对称下与实验相当一致的光谱，且得到可用于其他性质的计算的各态波函数 关键词：     

ArCN三原子准分子的研究(Ⅰ)——电子态的量子化学计算

分别采用６－３１Ｇ＊，６－３１Ｇ?＊基组对线性ＡｒＣＮ分子的X²∑⁺，Ａ²∏_i，Ｂ²∑⁺，Ｃ²∏_i，Ｄ²∑⁺和Ｅ²∏_r ６个电子态进行了从头计算法开壳自旋限制Ｈａｒｔｒｅｅ－Ｆｏｃｋ（ＲＯＨＦ）计算。计算结果表明线性ＡｒＣＮ分子的电子态具有典型的准分子结构，从而可以肯定ＣＮ与稀有气体原子Ｒｇ（Ａｒ，Ｋｒ，Ｘｅ）能够形成自由基准分子。对Ｘ²∑⁺，Ａ²∏_i的自旋非限制Ｈａｒｔｒｅｅ－Ｆｏｃｋ（ＵＨＦ）计算证实较大的自旋污染不影响势能曲线的形状。 关键词：     

类氦离子的KLL双电子复合过程的相对论理论研究

在相对论多组态Dirac-Fock理论基础上，发展了计算双电子复合截面的程序.并以类锂C³⁺，Ar¹⁵⁺，Kr³³⁺和U⁸⁹⁺等离子为例，详细计算了共振双激发态1s2l2l′的辐射衰变率、Auger衰变率及相应的双电子复合截面.对于C⁴⁺，Ar^l6+和Kr³⁴⁺离子的结果与已有的计算和实验结果都能很好地符合；对于U⁹⁰⁺离子，则重点 关键词： 双电子复合 截面 MCDF     

GdOBr∶Eu晶场参数与自由离子参数的高压研究

在GdoBr∶Eu的常压和高压荧光谱实验数据基础上，对晶场能级及其重心进行了拟合计算，得到了晶场参数和自由离子参数（Slater参数和自旋 轨道耦合参数）在高压下的变化情况．计算结果表明，随压力增大，晶场参数B⁴₀，B⁶₀增大，B⁶₄减小，B²₀，B⁴₄的变化有些起伏．晶场强度在8GPa以 关键词：     

LaFe11.5Si1.5中的磁不稳定性

通过对LaFe_11.5Si_1.5化合物进行自旋极化和固定磁矩(FSM)的能带 计算，发现LaFe_11.5Si_1.5化合物具有磁不稳定性的特征，无磁态和铁磁 态的能量 差别很小，FSM计算表明LaFe_11.5Si_1.5化合物具有低自旋态和高 自旋态的双 磁性态特征，在一定条件下能够在两磁性态之间发生变磁转变.通过计算的结果，定性地分 析了实验上所观察的一些现象. 关键词： 磁不稳定性 变磁转变     

嵌入原子法研究Ni3Al中点缺陷以及Re择优占位和集团化

基于纯金属元素Ni，Al和Re的基本物理性质，建立了一个Ni-Al-Re三元体系的分析型嵌入原子多体势.结合分子动力学计算了Ni₃Al的平衡晶格常数、弹性模量、结合能、空位形成能以及反位置缺陷形成能，并分析了Ni₃Al中点缺陷的存在形式.计算结果表明，当成分偏离理想化学配比时出现反位置缺陷.同时研究了Re在Ni₃Al中的择优占位以及Re在Ni₃Al和Ni中的集团化行为.计算结果表明，Re在Ni₃Al中优先置换Al的位置，且发现当Re原子团的尺寸接近于11?时，Re原子团的长大趋势变弱.计算结果与实验以及其他的理论计算结果相符合. 关键词： 嵌入原子势 3Al')" href="#">Ni₃Al Re 占位 集团化     

V+注入锐钛矿TiO2第一性原理研究

用金属离子注入方法在锐钛矿TiO₂薄膜中掺杂了V⁺，采用全势线性缀加平面波方法计算了锐钛矿TiO₂及V⁺掺杂TiO₂超原胞的电子结构，通过紫外-可见吸收光谱测试方法检测了注入不同剂量的V⁺对TiO₂薄膜吸收光谱的影响.理论计算和实验结果表明，锐钛矿TiO₂薄注入V⁺后，带隙宽度变小，吸收光谱发生红移，并且TiO 关键词： +注入')" href="#">V⁺注入 2')" href="#">TiO₂ 全势线性缀加平面波方法 能带结构     

插层化合物LixTiS2中Li离子-空位二维有序结构稳定性的第一性原理研究

根据局域密度近似下的密度泛函理论，用第一性原理方法对TiS₂，LiTiS₂和Li_xTiS₂(x=1/4, 1/3, 1/2, 2/3, 3/4)有序系统进行了几何优化和总能量计算.将计算结果与已有的实验和理论结果进行了对比，得到的归一化结构参量增量Δa₀和Δc₀随离子浓度单调地增加，与实验结果符合较好.Li_{关键词： x}TiS₂')" href="#">Li_xTiS₂ 有序结构 第一性原理计算 密度泛函理论     

Co2+离子在MgF2和ZnF2晶体中的各向异性g因子的理论研究

利用基于基团模型的3d⁷离子在斜方对称中的高阶微扰公式计算了MgF₂和ZnF₂晶体中Co²⁺杂质中心的各向异性g因子g_x，g_y和g_z. 在计算中，考虑了共价效应， 组态相互作用和斜方晶体场的贡献；而且与此相关的参量可由所研究的晶体的光谱和结构数据得到. 计算结果与实验符合较好.     

飞机跑道胶痕的自动识别系统设计与实现

为了减轻机场跑道除胶工作人员的劳动强度,提高除胶工作效率,文章提出了一种基于机器视觉的胶痕自动查找和识别方法,设计了基于ARM单片机控制的图像无线采集和基于PC机控制的图像接收、图像预处理和图像识别系统。文章通过分析预处理后的数据特点,确定了基于细胞神经网络算法的胶痕识别算法,然后在MATLAB仿真环境下确定了该算法的最优模型和参数,最后在Visual C++ 6.0环境下完成了该算法的程序编译,调试并完成了对胶痕的自动识别过程。理论仿真和程序测试的结果证明了文章提出的方法在胶痕自动识别系统中的可行性,也为机场特种设备的无人化和智能化提供了参考。     

Ca和Ce双原子复合填充p型CamCenFexCo4－xSb12化合物的合成及热电性能

用高温熔融法合成了Ca和Ce复合填充的单相p型Ca_mCe_nFe_{xCo4-xSb12化合物，探索了两种原子复合填充对其热电性能的影 响规律.研究结果表明，填充分数相同时，Ca和Ce两种原子复合填充的p型CamCe nFexCo4-xSb12化合物的载流子浓度和电 导率介于Ca或Ce一种原子单独填充的化合物之间，且随两种原子填充分数m+n的增加而降低 ；赛贝克系数随两种原子填充总量，尤其是Ce填充分数m的增加以及温度的上升而增加；在 相同填充分数时，两种原子复合填充的p型CamCenFexC o4-xSb12化合物的晶格热导率较Ca或Ce一种原子单独填充的化合物 的晶格热导率低，当总填充分数m+n为0.3左右，且Ca和Ce的填充量大致相等时，化合物的晶 格热导率最低.p型Ca0.18Ce0.12Fe1.45Co2.55Sb12.21化合物的最大热电性能指数ZT值在750K时达到1.17. 关键词： skutterudite化合物 双原子复合填充 合成 热电性能}     

Catalytic effect of water,water dimer,water trimer,HCOOH, H2SO4, CH3CH2COOH and HN(NO2)2 on the isomerisation of HN(NO2)2 to O2NNN(O)OH: a mechanism study

In this article, the isomerisation mechanisms of HN(NO₂)₂ to O₂NNN(O)OH without and with catalyst X (X = H₂O, (H₂O)₂, (H₂O)₃, HCOOH, H₂SO₄, CH₃CH₂COOH and HN(NO₂)₂) have been investigated theoretically at the CBS-QB3 level of theory. Our results show that the catalyst X (X = H₂O, (H₂O)₂, (H₂O)₃, HCOOH, H₂SO₄ and CH₃CH₂COOH) shows different positive catalytic effects on reducing the apparent activation energy of the isomerisation reaction processes. Such different catalytic effects are mainly related to the number of hydrogen bonds and the size of the ring structure in X (X = H₂O, (H₂O)₂ and (H₂O)₃)-assisted transition states, as well as different values of pK_a for H₂SO₄, HCOOH and CH₃CH₂COOH. Very interesting is also the fact that H₂SO₄-assisted reaction is the most favourable for the hydrogen transfer from HN(NO₂)₂ to O₂NNN(O)OH, due to the smallest pK_a (?3.0) value of H₂SO₄ than H₂O, HCOOH, H₂SO₄ and CH₃CH₂COOH, and also because of the largest ∠X???H???Y (the angle between the hydrogen bond donor and acceptor) involved in H₂SO₄-assisted transition state. Compared to the self-catalysis of the isomerisation mechanisms of HN(NO₂)₂ to O₂NNN(O)OH, the apparent activation energy of H₂SO₄-assisted channel also reduces by 9.6 kcal?mol^?1, indicating that H₂SO₄ can affect the isomerisation of HN(NO₂)₂ to O₂NNN(O)OH, most obvious among all the catalysts H₂O, (H₂O)₂, (H₂O)₃, HCOOH, H₂SO₄, CH₃CH₂COOH and HN(NO₂)₂.     

Surface modification of Mg2B2O5 whisker and its effect on the mechanical properties and thermostability of polycarbonate/Mg2B2O5w composites

The Mg₂B₂O₅ whiskers (Mg₂B₂O₅w) were modified by boric acid ester (BE) coupling agent and used to prepare polycarbonate (PC) composites. Surface wettability test and evaluation of dispersibility of BE-modified Mg₂B₂O₅w (BE-Mg₂B₂O₅w) in n-heptane were carried out by water contact angle measurement and polarizing microscopy, respectively. The surface chemical characteristics of BE-Mg₂B₂O₅w and estimation of the amount of tightly bonded organic modifier were examined by Fourier transform infrared spectrometry (FT-IR) and thermogravimetric analysis (TGA), respectively. The influence of BE-Mg₂B₂O₅w on the mechanical property, morphology and thermostability of PC composites was investigated by using universal testing machine, scanning electron microscopy (SEM), dynamic mechanical analysis (DMA) and TGA, respectively. It was found that BE was successfully grafted to the surface of Mg₂B₂O₅w, and the hydrophobic BE-Mg₂B₂O₅w leads to high ratio of adhesion work to interfacial tension between PC and BE-Mg₂B₂O₅w, and its better dispersibility in n-heptane. Furthermore, the incorporation of BE-Mg₂B₂O₅w into PC matrix resulted in higher tensile properties of PC/BE-Mg₂B₂O₅w than that of PC/Mg₂B₂O₅w composites and lower maximum weight loss rate than that of PC. The storage modulus of the PC/Mg₂B₂O₅w composites increased obviously as a function of whisker content, especially for the composites with BE-Mg₂B₂O₅w, but the T_g value changed little.     

Raman characterizations and structural properties of the binary TeO2?WO3, TeO2?CdF2 and ternary TeO2?CdF2?WO3 glasses

The Raman spectroscopy technique was used to characterize the microstructure and the crystallization properties of the as‐cast and heat‐treated binary TeO₂ WO₃, TeO₂ CdF₂ and ternary TeO₂ CdF₂ WO₃ glasses and glass ceramics. The results were compared with those obtained by using the X‐ray diffraction technique. The effect of the WO₃ and CdF₂ contents on the TeO₂ glass network and the intensity ratios of the deconvoluted Raman peaks were determined. The shifts in the Raman band wavenumbers and the intensity values for each band were investigated. The Raman results indicated that the glasses were mainly formed by the [TeO₄] and [TeO₃] units. The [TeO₄] units convert to [TeO₃] units with the addition of WO₃ and CdF₂ into tellurite glasses. All the crystalline phases such as α‐TeO₂, δ‐TeO₂ and γ‐TeO₂ existing in the TeO₂ WO₃, TeO₂ CdF₂ and TeO₂‐ WO₃ CdF₂ glasses were determined. The transformation of the metastable γ‐TeO₂ phase into stable α‐TeO₂ was observed for the (1 − x)TeO₂ xWO₃ (where x = 0.15, 0.20, 0.25), 0.90Te₂ 0.10CdF₂, the 0.85TeO₂ 0.10CdF₂ 0.05WO₃ and 0.80TeO₂ 0.10CdF₂ 0.10WO₃ glasses, and the transformation of the metastable δ‐TeO₂ phase into the stable α‐TeO₂ was also observed for the TeO₂ CdF₂ WO₃ glass system. In addition, an unidentified phase formation, labeled ε, was determined. Copyright © 2009 John Wiley & Sons, Ltd.     

SrBi2Ta2O9/Bi4Ti3O12复合铁电薄膜的制备与特性研究

采用溶胶凝胶工艺在p-Si衬底上制备了SrBi₂Ta₂O₉/Bi₄Ti₃O₁₂复合铁电薄膜. 研究了SrBi₂Ta₂O₉/Bi₄Ti₃O₁₂复合薄膜的微观结构与生长行为、铁电性能和疲劳特性. 研究表明: Si衬底Bi₄Ti< 关键词： 2Ta₂O₉')" href="#">SrBi₂Ta₂O₉ 4Ti₃O₁₂')" href="#">Bi₄Ti₃O₁₂ 复合铁电薄膜 溶胶凝胶工艺     

Effects of coating parameters on the morphology of SiO2-coated TiO2 and the pigmentary properties

SiO₂-coated TiO₂ powders were prepared by the chemical deposition method starting from rutile TiO₂ and Na₂SiO₃. The SiO₂-coated TiO₂ powders were characterized by X-ray photoelectron spectroscopy, Zeta-potential analysis, Fourier transform infrared spectroscopy, and transmission electron microscopy. The evolution of island-like and uniform coating layers was found to depend upon the ratio of Na₂SiO₃ to TiO₂, reaction temperature, and pH. The whiteness and brightness of the SiO₂-coated TiO₂ powders increased in response to an increase in the SiO₂ loading, but there was a maximum value among the light scattering indexes. The SiO₂-coated TiO₂ powders possessed more negative Zeta potentials than the naked TiO₂. The dispersibility of the SiO₂-coated TiO₂ powders with the continuous and uniform SiO₂ coating layers was higher than that of the naked TiO₂ and the SiO₂-coated TiO₂ powders with the island-like SiO₂ coating layers.     

Effect of some additions on the sinterability and magnetic properties of barium hexaferrite

The effect of additions on the densification of previously prepared stoichiometric barium hexaferrite, during the initial and intermediate stages of sintering, as well as on the coercivity and remanence were studied. The effect of non-stoichiometry, SiO₂, Al₂O₃, Cr₂O₃, TiO₂, SnO₂, MnO₂, MgO, NiO and Bi₂O₃ is included.While SiO₂ and Bi₂O₃ form liquid phases that increase the density, Al₂O₃, Cr₂O₃ and MnO₂ form a limited solid solution and are generally beneficial when added in the proper amounts. At 1300 SiO₂ up to 0.55% and Al₂O₃ up to 1% gave better magnetic properties. On the other hand addition of TiO₂, MgO, NiO or SnO₂ has a deleterious effect.     

Structure of Artificial Grain Boundaries in Sapphire Bicrystals with Intermediate Layers

The structure of the artificial grain boundaries in Al₂O₃ bicrystals withY₃Al₅O₁₂ and Y-stabilizedZrO₂ (Y-ZrO₂) intermediate layers was studiedwith high resolution electron microscopy, electron diffraction and energydispersive X-ray analysis. TheY₃Al₅O₁₂ intermediate layer wasfound to be polycrystalline with three different orientation relationshipsbetween the ₂O₃ and theY₃Al₅O₁₂. The structure of theY₃Al₅O₁₂/₂O₃ interfaces is described.Also₂O₃ bicrystals with an Y-ZrO₂/₂O₃/Y-ZrO₂/₂O₃/Y-ZrO₂intermediate layer, prepared at two different temperatures, werestudied.Recry stallization of the intermediate layers occurred during thesolid phase intergrowth of the ₂O₃ bicrystalsparts and only an Y-ZrO₂ layer was found as intermediatelayer. The misorientation between the consecutive Y-ZrO₂grains was less than 1.5°. Misfit dislocations and atomic height stepsdecorate the Y-ZrO₂/₂O₃interface.     

Effect of heat treatment on the structure and the thermoelectric properties of Sb<Subscript>0.9</Subscript>Bi<Subscript>1.1</Subscript>Te<Subscript>2.9</Subscript>Se<Subscript>0.1</Subscript> thin films and composites based on them

This work considers the effect of vacuum annealing on the thermoelectric properties of Sb_0.9Bi_1.1Te_2.9Se_0.1 thin film and Sb_0.9Bi_1.1Te_2.9Se_0.1–C composites with various carbon contents produced by ion-beam deposition in an argon atmosphere. The electrical resistivity and the thermopower of Sb_0.9Bi_1.1Te_2.9Se_0.1–C nanocomposites are found to be dependent on not only the carbon concentration but also the type and the concentration of intrinsic point defects of the Sb_0.9Bi_1.1Te_2.9Se_0.1 solid solution, which determine the type of conductivity of Sb_0.9Bi_1.1Te_2.9Se_0.1 granules. The power factors are estimated for films of Sb_0.9Bi_1.1Te_2.9Se_0.1 solid solution and films of Sb_0.9Bi_1.1Te_2.9Se_0.1–C composites and found to have values comparable with the values for nanostructured materials on the basis of (Bi,Sb)₂(Te,Se)₃ solid solutions.