La_(1-x)Nd_xCrO_3(0.0≤x≤1.0)的化学键参数计算

使用复杂晶体化学键理论计算了La1-xNdxCrO3 (x =0 .0 ,0 .2 ,0 .4,0 .6 ,0 .8,1.0 )的化学键参数 ,如键性、键极化率等。结果表明 ,La-O ,Nd -O和Cr-O键的共价性基本上不随Nd掺杂的变化而变化 ,这个结论与实验结果一致。键极化率和磁距则随着掺杂量的增加而增加。共价性的大小次序为La -O 相似文献   

La0.7-xDyxSr0.3MnO3(0.00≤x≤0.70)的TCR研究

研究了La位Dy掺杂对La0.7-xDyxSr0.3MnO3(0.00≤x≤0.70)电阻温度系数(TCR)的影响.实验结果表明:Dy掺杂将引起电阻率曲线的急剧变化,导致出现大的TCR;随Dy掺杂的增加,TCR在x=0.30出现峰值,然后随掺杂量的增加逐步降低.体系出现大的TCR,来源于Dy掺杂引起的晶格畸变和额外磁性耦合.     

K X-ray relative transition probabilities for 23≤Z≤33

The K X-ray relative transition probabilities K_b/K_a of some elements for atomic numbers 23Z33 induced by 3 MeV protons were measured. The experimental results are compared with the relativistic Hartree-Fock (RHF) calculations. Good agreements have been obtained considering the experimental error.     

K+掺杂对钙钛矿氧化物La0.7Sr0.3-xKxMnO3(0.05≤x≤0.3)的结构及磁性的影响

钙钛矿;双交换作用;居里温度;最大磁熵变     

HNO与(HF)1≤n≤3分子间的蓝移与红移氢键

运用量子化学从头算方法研究了HNO与分子簇(HF)1≤n≤移氢键, 重极化与重杂化和分子内超共轭导致了氢键的蓝移; 所有的X…H—F(X=O, N, F)氢键都是红移的, 分子间超共轭导致了氢键的红移. 在多分子体系形成的氢键链中, 分子间超共轭作用呈现规律性递变, 它导致了氢键强度与频率位移的规律性变化, 电子密度拓扑分析结果反映和支持了这种规律性变化.     

HNO与（HF）1≤n≤3分子间的蓝移与红移氢键

运用量子化学从头算方法研究了HNO与分子簇(HF)1≤n≤3形成的蓝移与红移氢键.在这些体系中,F…H-N都是蓝移氢键,重极化与重杂化和分子内超共轭导敛了氰键的蓝移;所有的X…H-F(X=O,N,F)氢键都是红移的,分子问超共轭导致了氢键的红移.在多分子体系形成的氢键链中,分子问超共轭作用呈现规律性递变,它导致了氢键强度与频率位移的规律性变化,电子密度拓扑分析结果反映和支持了这种规律性变化.     

Electron Excited M X-Ray Spectra of the Elements 55≤Z≤58

The M emission spectra of the elements 55 Cs, 56 Ba, 57 La, and 58 Ce were measured using wavelength dispersive X-ray spectrometry with a TAP crystal as the dispersing element. In total, 34M lines were observed, of which only 13 are contained in the compilation of Bearden. M and M of 56 Ba are among the new lines. They have their origin in a similar process to one that is known for 57 La. The interpretation of these spectra is complicated by the strong overlap of some emission lines with the M_IV,V absorption structures, which may lead to anomalous self-absorption effects. Therefore, we have concentrated on spectra taken at a low energy of the exciting electrons, E₀=2.5keV. However, in order to illustrate the anomalous self-absorption effects parts of the 2.5keV spectra, of Ba and La, are shown in comparison with the 10keV spectra.     

Syntheses and Single-crystal Structures of Er3GexGeS7 （1/4≤x≤ 1/2）

As part of our systematic research on the acentric rare earth chalcogenides, the ErAlGeS5/KBr, Er3AgGeS7/KBr and Er6Ge3S14/KBr systems were investigated and three compounds belonging to the R6B2C2Q14 （R = rare earth, B = 6-coordinated element, C = 4-coordinated element, Q = S and Se） family were identified. These compounds crystallize in the P63 space group, and the crystal data are as follows： Er3Ge1/4GeS7, a = 9.6480（14）, c = 5.7920（12） A^°, Z = 2; Er3Ge0.382（8）GeS7, a = 9.6360（14）, c = 5.8460（12） A^°, Z = 2; Er3Ge1/2GeS7, a = 9.6061（13）, c = 5.8346（18）A^°, Z = 2. Single-crystal analysis indicated that the Er3GexGeS7 （x = 1/4, 0.382（8）, 1/2） structures consist of three types of building blocks： ErS7, GeS4 and GeS6 units. Er3MxGeS7 are deficient compounds with the B sites occupied partly by Ge（Ⅳ） and/or Ge（Ⅱ）.     

La1-xCexSrNiO4(0≤x≤0.7)的合成、表征及Nox分解催化性能的研究

采用柠檬酸法合成了一系列含Ce的La1-xCexSrNiO4,发现Ce在A位的取代量能够达到30%.大量Ce取代La后,不仅改善了无氧条件下对NO分解的活性,还提高了LaSrNiO4在有氧条件下的催化活性.在体积分数为6.0%的O2存在下,La0.7Ce0.3SrNiO4对NO分解比活性高达1.58 μmol/(s·m2)(1 123 K),表明La1-xCexSrNiO4是一种很有潜力的NO消除催化剂.     

LaNi_(3.8-x)Al_x(0≤x≤0.5)多相储氢合金的结构及电化学性能

采用真空电弧熔炼法制备了LaN i3.8-xA lx(0≤x≤0.5)储氢合金,并在氩气气氛中进行退火处理。通过X射线衍射(XRD),S ievert′s方法和电化学测试分别分析了合金的物相结构、储氢和电化学性能。研究结果表明:LaN i3.8-xA lx(0≤x≤0.5)合金主要由LaN i5,Ce2N i7,Pr5Co19和Ce5Co19型相组成。随着A l的变化,各相相丰度发生变化,而相丰度的变化影响了合金的滞后和吸/放氢平台压力。随着x的增加,LaN i3.8-xA lx(0≤x≤0.5)合金的放电容量先增大至270 mAh.g-1(x=0.3),然后缓慢降低;在x=0.3时合金显示出较好的充/放电循环稳定性。极化电阻和电化学交流阻抗则随着x的增加缓慢降低,交换电流密度增大,导致高倍率放电有所增大。     

Configuration of the surface atoms in AlN (270 ≤ N ≤ 500) clusters

Configuration of the surface atoms in aluminum clusters was investigated based on the structures with global minimum potential energy of some Al clusters in the size range of 270-500. The structures were optimized by the dynamic lattice searching with constructed cores (DLSc) method with the NP-B potential. In the optimized structures, all clusters are identified as truncated octahedra (TO) including three complete TO at Al(260), Al(314), and Al(405). With the model of TO(260) and TO(405), the configurations of the surface atoms in the structures of the clusters from 261 to 314 and from 406 to 459 were investigated. The sites on (100) faces are found to be preferable to those on (111) faces for locating the new atoms with the increase of the cluster size, but for the clusters larger than 405 atoms, the sites on the (111) face are favored when the number of atoms exceeds the site number of a (100) face. Furthermore, the sites on the edge adjoining a (100) face and a (111) face are found to be very important to make a cluster more stable.     

L X-ray intensity ratios of some elements in the region of 56≤Z≤83

L X-ray intensity ratios of Ba, La, Ce, Gd, Er, Yb, Ta, Au, Hg, Pb, Bi have been measured. The L shell elctrons are excited by 59.5 keV gamma-rays from ²⁴¹ Am and the L X-rays from samples are measured with a Si(Li) detector. The experimental values are compared with the theoretical values of the pure elements.     

BaCe0.8-xNbxGd0.2O3-δ(0≤x≤0.45)的制备及性能研究

采用高温固相反应法制备了质子导体BaCe_0.8-xNb_xGd_0.2O_3-δ(0≤x≤0.45)。结合XRD、SEM、EIS等技术对其物相、微观形貌、稳定性及电导率进行了研究。结果表明,在1 600 ℃烧结5 h制备的质子导体BaCe_0.8-xNb_xGd_0.2O_3-δ(0≤x≤0.45)均能保持主相为斜方晶的钙钛矿结构。Nb的加入可明显提高烧结样品的致密性及在CO₂和水蒸气气氛下的稳定性。在湿润H₂/Ar(0.4%,V/V)气氛中800 ℃下,x=0.1样品的电导率为5.73 mS·cm^-1,电导活化能为0.35 eV,与x=0的样品相当。     

Calculation of average L shell fluorescence yields for the elements with 25≤Z≤101

Average L shell fluorescence yield , average L shell Auger yields and the total L shell X-ray fluorescence (LXRF) cross sections (σ _L ^x ) at 30 keV have been calculated theoretically for the elements with 25≤Z≤101. These calculated values have been compared with the other experimental and theoretical values.     

Structural Distortion in Perovskite Type KCaH3–xFx (0.54 ≤ x ≤ 3)

Representatives of the solid solution series KCaH_3–xF_x were synthesized by solid state reactions from binary metal hydrides and fluorides. Crystal structures were analyzed by Rietveld refinement based on X-ray powder diffraction. The degree of substitution was determined by refinement of site occupancy factors as well as elemental analysis for hydrogen. Three sections of x in KCaH_3–xF_x can be distinguished. For x < 0.54 no hydride fluoride exists, i.e. there is no hydride of the composition KCaH₃ and the solid solution starts only at x = 0.54. The tetragonal SrTiO₃ type structure with partial ordering of hydrogen and fluorine atoms is found for 0.54 ≤ x ≤ 1.7. Both anion positions show mixed occupation with some preference of hydrogen atoms for 8h and fluorine atoms for 4a sites (I4/mcm, SrTiO₃ type). For fluorine-rich compounds a solid solution with orthorhombic GdFeO₃ type structure (Pnma) and a perfectly statistical distribution of hydrogen and fluorine atoms is found (1.8 ≤ x ≤ 3). Interatomic distances resulting from the structure refinements are in the range of typical K–H, K–F, Ca–H, and Ca–F distances for mainly ionic compounds.     

新型固体电解质Ce6- x Sm x MoO15- δ (0≤x≤1.2)的合成及电性质

采用溶胶-凝胶方法合成系列新型氧化物 Ce6- x Sm x MoO15- δ (0≤x≤1.2). 通过TG-DTA, XRD和XPS等手段对氧化物结构进行了表征. 结果表明, 氧化物的最低成相温度为400 ℃, 具有立方莹石结构. Sm的掺杂可增加氧离子空位浓度, 改善母体电导率. 阻抗谱表明, 采用溶胶-凝胶法合成固体电解质可减少或消除其晶界电阻. 800 ℃时, Ce5.2Sm0.8MoO15- δ的电导率高达6.67×10-3 S/cm.     

(Ce0.9Nd0.1)1-xMoxO2-δ(0.00≤x≤0.10)的合成、表征与电性能

采用溶胶-凝胶法合成(Ce0.9Nd0.1)1-xMoxO2-δ(x=0.00、0.02、0.05、0.10)氧化物,通过X射线衍射(XRD)、场发射扫描电镜(FESEM)等手段对氧化物进行结构表征,交流阻抗谱测试电性能.结果表明:所有样品均为单一萤石立方结构;少量MoO3的加入提高了材料的致密性,降低了材料的总电阻、晶界电阻和晶界电阻在总电阻中所占比例,提高了材料的电导率.1200 ℃烧结样品24 h,测试温度700℃时,(Ce0.9Nd0.1)1-xMoxO2-δ(x=O.00)总电导率和晶界电导率分别为0.05和O.19 S·m-1,掺Mo材料(Ce0.9Nd0.1)1-xMoxO2(x=0.02)的总电导率和晶界电导率分别为2.42和3.96 S·m-1.     

基于链状SemSn(2≤m+n≤4)小分子的硒硫碳复合正极材料的制备及其电化学性能

将Se固溶复合到链状小硫分子S_2~4中,利用超微孔碳(UMC)的空间限域效应,在UMC中成功构建了链状Se_mS_n(2≤m+n≤4)小分子,并用作锂硫(Li-S)电池正极材料。与链状S_2~4小分子相比,改性后的Se_mS_n(2≤m+n≤4)小分子电导率更高,锂化能更低,放电锂化过程更容易。所制得的UMC/Se_mS_n(2≤m+n≤4)复合正极材料的放电过程为一步固相转化反应,从而有效抑制了活性物质的穿梭流失。与UMC/S_2~4复合正极材料相比,UMC/Se_mS_n(2≤m+n≤4)复合正极材料的电荷传递阻抗更小,放电比容量更高。因此,UMC/Se_mS_n-40(2≤m+n≤4,w_SeS2∶w_UMC=4∶6)复合正极材料在0.1C时循环100次后,比容量依然保持有844 mAh·g^-1;在0.5C下长时间循环500次时,每次循环容量损失仅约为0.07%,表现出优异的循环稳定性。     

K β /K α X-ray intensity ratio in the region of 15≤Z≤22

The X-ray intensity ratioK /K has been measured by using a 10 mCi⁵⁵Fe source (MnK X-rays) and high resolution Si(Li) detector system coupled to a computer-controlled multichannel analyzer over the range of 15Z22. Corrections have been made to the measured relative intensities (K andK X-rays) for self-absorption in the sample, air, Be-window absorption and detection efficiency. The results are compared with those of other experiments and with the Scofield calculations.     

Global minimum structures and structural phase diagrams of modified Morse clusters: 11 ≤ N ≤ 30

The energetically favored structures of clusters are determined by the interactions among particles. Using the modified Morse pair potential, which has two parameters that can freely control the interactions at the minimum, short range, and long range, we systematically investigated how the interactions determines the global minimum structures of clusters and gave the structural phase diagram at 0 K for each cluster size at the range 11 ≤ N ≤ 30. Compared to the Morse potential, a number of new structures are found, and some of them are unexpected. The global minimum structures of modified Morse clusters can act as structural bank, which will be helpful in the optimization of certain real clusters.