Y2(Fe1-x-y,Coy,Crx)17化合 物的结构及居里温度

通过x射线衍射及磁测量手段研究了Y₂(Fe_1-y-x,Co_y,C r_x)₁₇化合物的结 构及居里温度.研究结果表明Y₂(Fe_1-y-x,Co_y,Crx)₁₇化合物具有六 角相的Th₂Ni₁₇型结构.随着x的增加，Y₂(Fe 关键词： 2(Fe_1-y-x')" href="#">Y₂(Fe_1-y-x y')" href="#">Co_y x)_{1 7}化合物')" href="#">Cr_x)_{1 7}化合物 x射线衍射 居里温度     

三角对称下3d3离子2E态g因子性质研究

采用完全对角化方法,以尖晶石结构的ZnAl₂Ｏ₄:Cr^3＋,ZnGa₂Ｏ₄:Cr^3＋和MgAl₂Ｏ₄:Cr^3＋系列晶体为例,联系晶格局域结构,对三角对称下3d³离子²E态g因子性质进行了研究.研究中考虑了包括自旋与自旋相互作用、自旋与另一轨 关键词： 2E态g因子')" href="#">²E态g因子 3离子')" href="#">3d³离子 尖晶石结构 磁相互作用     

在氧-水蒸气存在下单相Sr2(Gd,Ce)2Cu2RuO10的合成及其电学性质

传统固相反应所合成的锶系钌铜氧化物，通常总伴有少量铁磁性SrRuO₃杂相.采 用氧(或空 气)_水蒸气混合气氛下的新型固相反应，既能成功合成锶系钌铜氧化物的前驱物纯相Sr₂G dRuO₆(211相), 也能进一步在相对低的温度下成功合成锶系钌铜氧1222纯相化 合物RuSr₂(Gd,Ce)₂Cu₂O₁₀ (Ru_1222）， 使其中SrRuO _{关键词： 水蒸气参与的新型固相反应 2}(Gd')" href="#">RuSr₂(Gd 2Cu_{2< /sub>O10纯相')" href="#">Ce)2Cu2< /sub>O10纯相 3杂相')" href="#">SrRuO3杂相 电学性质}     

(1-x)(K0.5Na0.5)NbO3-xSrTiO3陶瓷的弛豫铁电性能

通过对（1-x）（K_0.5Na_0.5）NbO₃-xSrTiO₃（0≤x≤0.15）陶瓷的相组成、晶体结构和介电性能的研究发现,该陶瓷为单一的钙钛矿结构相.当x含量较小（x＜0.1）时为正交相结构,x≥0.1时转变为四方相结构.随着SrTiO₃掺杂量的增加,样品的致密度增加,样品由正常铁电相逐渐向弥散铁电相转变,且相 关键词： 弛豫铁电体 0.5Na_0.5）NbO₃铁电陶瓷')" href="#">（K_0.5Na_0.5）NbO₃铁电陶瓷 3掺杂')" href="#">SrTiO₃掺杂 相变温度     

OsnN0,±(n=1—6)团簇几何结构与稳定性的理论研究

采用密度泛函理论(DFT)中的B3LYP方法,在Lanl2dz基组水平上对(Os_nN)^0,±(n=1—6)团簇的各种可能构型进行了几何参数全优化,得到了它们的基态构型;并对基态构型的平均结合能(E_b) 、二阶能量差分(Δ₂E_n) 、解离能(E_d)和能隙(E_g)进行了理论研 关键词： nN^{0')" href="#">Os_nN0 (n=1—6)团簇')" href="#">±(n=1—6)团簇 几何结构 稳定性 密度泛函理论}     

Ni75Cr25-xAlx合金中L12相和D022相形核孕育期的微观相场模拟

基于微观相场动力学模型,运用原子图像、平均长程序参数和平均成分偏离序参数,研究了Al浓度对Ni₇₅Cr_25-xAl_x合金中L1₂相和D0₂₂相形核孕育期的影响以及孕育期与沉淀相析出顺序之间的关系.结果表明,L1₂相和D0₂₂相的形核孕育期不仅与Al浓度有关,而且与两相析出的先后顺序密切相关.当Al浓度小于7.5%时,先析出相为D0₂₂相,随着Al浓度的增大,D0₂₂相形核孕育期延长,后析出的L1₂相的形核孕育期也延长,L1₂相的原子簇?聚?速度加快;当Al浓度大于7.5%时,先析出相为L1₂相,随着Al浓度的增大,L1₂相的形核孕育期缩短,后析出的D0₂₂相形核孕育期也缩短.当Al浓度为7.5%时,L1₂相和D0₂₂相几乎同时析出,两者的孕育期没有明显的差别. 关键词： 形核孕育期 序参数 沉淀 微观相场模拟     

Si1-xGex合金半导体中CiCs和CiOi缺陷随Ge含量的变化

采用从头计算(ab initio)的方法对Si和Si_1-xGe_x合金半导体材料中C_iC_s缺陷的性质进行探讨,同时也对比调查了C_iO_i缺陷在Si和Si_1-xGe_x合金中的性质. 在不同Ge含量的Si_1-xGe_{x关键词： 1-x}Ge_x合金')" href="#">Si_1-xGe_x合金 从头计算法 iC_s缺陷')" href="#">C_iC_s缺陷 iO_i缺陷')" href="#">C_iO_i缺陷     

R3(Fe1-xCox)29-yCry(R=Gd,Sm)化合物相稳定性研究

在制备出Gd₃(Fe_1-xCo_x)_29-yCr_{y化合物基础上，成功制备出Sm3(Fe1-xCox)29 -yCry化合物，通过x射线衍射和热磁分析对R3(Fe1-x< /sub>Co x)29-yCry 关键词： 3(Fe1-xCox)29-yCry化合物')" href="#">R3(Fe1-xCox)29-yCry化合物 相结构 单轴磁晶各向异性}     

(Nd1－xGdx)3Fe27.31Ti1.69化合物的结构和磁性

通过X射线衍射和磁性测量等手段研究了(Nd_1-xGd_x)₃Fe_27.31Ti_1.69(0≤x≤0.6)化合物的结构和磁性.X射线衍射测量结果表明Gd替代后并未改变Nd₃(Fe,Ti)₂₉化合物的晶体结构，但引起了晶胞体积收缩.随着Gd含量的增加，化合物的居里温度T_C和室温磁晶各向异性场B_a单调增加，而自旋重取向 关键词： 1-xGd_x)₃Fe_27.31Ti_1.69化合物')" href="#">(Nd_1-xGd_x)₃Fe_27.31Ti_1.69化合物 磁晶各向异性 自旋重取向 磁相图     

Antisite defect types and temporal evolution characteristics of D0<Subscript>22</Subscript>-Ni<Subscript>3</Subscript>V structure: Studied by the microscopic phase field

Microscopic phase field simulation is performed to study antisite defect type and temporal evolution characteristic of D0₂₂-Ni₃V structure in Ni₇₅Al _x V_25−x ternary system. The result demonstrates that two types of antisite defect V_Ni and Ni_V coexist in D0₂₂ structure; however, the amount of Ni_V is far greater than V_Ni; when precipitates transform from D0₂₂ singe phase to two phases mixture of D0₂₂ and L1₂ with enhanced Al:V ratio, the amount of V_Ni has no evident response to the secondary L1₂ phase, while Ni_V exhibits a definitely contrary variation tendency: Ni_V rises without L1₂ structure precipitating from matrix but declines with it; temporal evolution characteristic and temperature dependent antisite defect V_Ni, Ni_V are also studied in this paper: The concentrations of the both defects decline from high antistructure state to equilibrium level with elapsed time but rise with elevated temperature; the ternary alloying element aluminium atom occupies both α and β sublattices of D0₂₂ structure with a strong site preference of substituting α site. Supported by the National Natural Science Foundation of China (Grant Nos. 50671084 and 50875217), the Doctorate Foundation of Northwestern Polytechnical University of China (Grant No. CX200806), the China Postdoctoral Science Foundation Funded Project (Grant No. 20070420218), and the Natural Science Foundation of Shaanxi Province of China     

AlO2和Al2O分子的结构与解析势能函数

运用密度泛函理论的B3LYP方法在6-311++G^**水平上,对AlO₂,Al₂O分子的结构进行了优化计算,得到AlO₂,Al₂O分子的稳定结构都为D_∞h构型.　AlO₂电子态为X²Π_u,平衡核间距R_Al-O关键词： 2')" href="#">AlO₂ 2O')" href="#">Al₂O Murrell-Sorbie函数 多体项展式理论     

有机金属化学气相沉积法制备的Ni/Al2O3纳米复合材料的氢吸附

研究了通过有机金属化学气相沉积技术及单源分子前躯体方法制备的Ni/Al₂O₃纳米复合材料的氢吸附(存储). 在冷壁的有机金属化学气相沉积反应器中,通过降解Ni(acac)₂粉末基底上的[H₂Al(OtBu)]₂制备的Ni/Al₂O₃纳米复合材料. 通过X射线粉末衍射、扫描电镜、透射电镜以及能量色散型X射线荧光光谱等技术表征该复合材料. 采用自制Sievert's设备研究该复合材料的氢吸附(存储),可以储存约2.9%(重量比)的氢.     

Spin polarization effect of Ni2 molecule

The density functional theory （DFT） method （b3p86） of Gaussian 03 is used to optimize the structure of the Ni2 molecule. The result shows that the ground state for the Ni2 molecule is a 5-multiple state, symbolizing a spin polarization effect existing in the Ni2 molecule, a transition metal molecule, but no spin pollution is found because the wavefunction of the ground state does not mingle with wavefunctions of higher-energy states. So the ground state for Ni2 molecule, which is a 5-multiple state, is indicative of spin polarization effect of the Ni2 molecule, that is, there exist 4 parallel spin electrons in Ni2 molecule. The number of non-conjugated electrons is greatest. These electrons occupy different spatial orbitals so that the energy of the Ni2 molecule is minimized. It can be concluded that the effect of parallel spin in the Ni2 molecule is larger than that of the conjugated molecule, which is obviously related to the effect of electron d delocalization. In addition, the Murrell-Sorbie potential functions with the parameters of the ground state and other states of the Ni2 molecule are derived. The dissociation energy De for the ground state of the Ni2 molecule is 1.835 eV, equilibrium bond length Re is 0.2243 nm, vibration frequency we is 262.35 cm^-1. Its force constants f2, f3 and f4 are 1.1901 aJ.nm^-2, -5.8723 aJ.nm^-3, and 21.2505 aJ.nm^-4 respectively. The other spectroscopic data for the ground state of the Ni2 molecule ωeχe, Be and αe are 1.6315cm 2, 0.1141 cm^-1, and 8.0145× 10^-4 cm^-1 respectively.     

Thev2 andv5 bands of CD3Cl: Infrared spectra and stark patterns with hyperfine structure

Infrared spectra of theV ₂ andV ₅ bands of CD₃Cl have been recorded with a resolution of about 0.015 cm^–1 and assigned. Moreover Stark patterns of the trideuterated methyl chloride for two CO₂ laser lines with saturated Lamb dips have been analysed. Many new strong coincidences showing hyperfine structure are observed and assigned.     

Dy含量对红色长余辉发光材料Sr3Al2Ｏ6:Eu2＋,Dy3＋性能的影响

采用溶胶凝胶法制备了Sr₃Al₂Ｏ₆:Eu^2＋,Dy^3＋红色长余辉发光材料,利用X射线衍射仪对材料的物相进行了分析,结果表明,1200℃下制备的样品的物相为Sr₃Al₂Ｏ₆,少量的Eu和Dy掺杂没有影响样品的相组成.采用荧光分光光度计、照度计测定了样品的发光特性.结果表明Sr₃Al₂Ｏ关键词： 红色长余辉 3Al₂Ｏ₆')" href="#">Sr₃Al₂Ｏ₆ 溶胶凝胶法     

Studies of the g factors and the local structure of the orthorhombic Ni center in KTaO3 crystal

The local structure and the g factor (g_x, g_y, and g_z) of the Ni⁺ center in KTaO₃ are theoretically studied using the perturbation formulas of the g factors for a 3d⁹ ion in orthorhombically elongated octahedra. The orthorhombic field parameters are determined from the superposition model and the local geometry of the system. In view of the covalency, the contributions from the ligand orbital and spin–orbit coupling interactions are taken into account from the cluster approach. In the calculations, the orthorhombic center is attributed to Ni⁺ occupying the host Ta⁵⁺ site, associated with the nearest-neighboring oxygen vacancy V_O along the c-axis. Furthermore, the planar Ni⁺–O²⁻ bonds are found to experience the relative variation ΔR (≈0.076 Å) along the a- and b-axis, respectively, due to the Jahn–Teller effect and the size mismatching substitution of Ta⁵⁺ by Ni⁺. Meanwhile, the effectively positive V_O can make the central Ni⁺ displace away from V_O along the c-axis by about 0.20 Å. The calculated g factors based on the above local distortions show good agreement with the experimental data.     

The electrical characteristics of a 4H-silicon carbide metal-insulator-semiconductor structure with Al2O3 as the gate dielectric

A 4H-silicon carbide metal-insulator-semiconductor structure with ultra-thin Al₂O₃ as the gate dielectric, deposited by atomic layer deposition on the epitaxial layer of a 4H-SiC (0001) 8⁰N-/N+ substrate, has been fabricated. The experimental results indicate that the prepared ultra-thin Al₂O₃ gate dielectric exhibits good physical and electrical characteristics, including a high breakdown electrical field of 25 MV/cm, excellent interface properties (1×10¹⁴ cm^-2) and low gate-leakage current (I_G = 1 × 10^-3 A/cm^-2@E_ox = 8 MV/cm). Analysis of the current conduction mechanism on the deposited Al₂O₃ gate dielectric was also systematically performed. The confirmed conduction mechanisms consisted of Fowler-Nordheim (FN) tunneling, the Frenkel-Poole mechanism, direct tunneling and Schottky emission, and the dominant current conduction mechanism depends on the applied electrical field. When the gate leakage current mechanism is dominated by FN tunneling, the barrier height of SiC/Al₂O₃ is 1.4 eV, which can meet the requirements of silicon carbide metal-insulator-semiconductor transistor devices.     

组合结构化合物Ho2Ni7-xFex(x=0-3.0)的晶体结构、结构转变和磁性

在金属间化合物的结构演变中,原子尺寸因素起着重要的作用.由于密堆积效应,不同原子半径比的元素往往形成不同的结构.而自由电子填充于原子构成的晶体结构的间隙中,它对化合物的结构也有影响.基于组合结构化合物Ho2Ni7-xFex,结合原子尺寸与自由电子对晶体结构的不同影响,文章探讨一种单位体积内自由电子浓度的经验方法来判断Ho2Ni7-xFex化合物中两种异构体间的转变.随着Fe含量的增加,Ho2Ni7-xFex化合物先结晶成Gd2Co7型三方结构,然后结晶成Ce2Ni7型六方结构.利用Rietveld精修技术和磁测量,获得了化合物的晶体结构参数和饱和磁化强度.化合物晶胞常数随Fe含量增加而增加,饱和磁化强度则随之减少(dMs/dx=-2).分析结果表明,单位体积内自由电子浓度更高,化合物形成三方结构,反之则形成六方结构.     

Al2O3:V3+晶体局域结构及其自旋哈密顿参量研究

提出了解释掺杂离子局域结构畸变的配体平面移动模型，建立了此模型下晶体微观结构与自旋哈密顿参量之间的定量关系.在考虑自旋与自旋、自旋与另一电子轨道和轨道与轨道作用等微小磁相互作用的基础上，采用全组态完全对角化方法，对Al₂O₃晶体中V³⁺的局域结构和自旋哈密顿参量进行了系统的研究.结果表明，V³⁺掺入Al₂O₃晶体后，上下配体氧平面间距离增大了0.0060 nm.从而成功地解释了Al₂O₃:V³⁺晶体的自旋哈密顿参量.在此基础上，研究了三角晶场下3d²离子自旋哈密顿参量的微观起源.研究发现，自旋三重态对自旋哈密顿参量的贡献是主要的，微小磁相互作用对自旋哈密顿参量的贡献只与自旋三重态有关.