Geometries and electronic properties of AunPdm (n=1-4, m =-1, 0, 1) clusters

Possible conformers for AunPdm (n = 1-4, m = -1, 0, 1) clusters have been presented and studied by use of density functional theory. The results indicate that for n = 2, linear conformer with C-infinityv symmetry is the most stable for anion species, while for cation and neutral species, conformer with C-2v symmetry is the most stable. For n = 3, 4, conformers with C-2v symmetry (kite-shape) are energetically favored. The calculated electron affinities (EAs) and vertical detachment energies (VDEs) are in good agreement with experiments for n = 1-4. It is also interesting to note that for even n (n = 2, 4), the most stable conformers do not give the best agreement between calculated and experimental EA and VDE values, while for odd n (n = 3), the lowest energy conformer also gives the best agreement. The ionization potentials (IPs) of AunPd clusters are calculated as well.

Synthesis, characterization and electrical properties of the new solid electrolyte materials Ce6-xErxMoO15-delta (0.0 < x < 1.5)

A new series of oxides, Ce6-xErxMoO15-delta (0.0 less than or equal to x less than or equal to 1.5), was synthesized using wet-chemistry techniques. The precursors and resultant oxide powders were characterized by differential thermal analysis/thermogravimetry, x-ray diffraction, and IR, Raman and x-ray photoelectron spectroscopy. The formation temperature of the powders was found to be as low as 350degreesC. Ce6-xErxMoO15-delta crystallized to a fluorite-related cubic structure. The electrical conductivity of the samples was investigated by using ac impedance spectroscopy. This showed that the presence of Er was related to the oxygen-ion conductivity, and that the highest oxygen-ion conductivity was found in Ce6-xErxMoO15-delta (x = 0.4), ranging from 5.9 x 10(-5) S cm(-1) at 300degreesC to 1.26 x 10(-2) S cm(-1) at 700degreesC, respectively. This kind of material shows a potential application in intermediate-temperature solid oxide fuel cells.

Y_(1.95-x)Gd_xSiO_5:Eu_(0.05)的真空紫外光谱

利用高温固相法合成了 Ｙ１．９５－ｘＧｄｘＳｉＯ５：Ｅｕ０．０５（ｘ＝０．６ｍｏｌ％）荧光体。结构测定表明所合成的荧光体为单斜晶系的Ｘ２型Ｙ２ＳｉＯ５相，空间群为Ｂ２／ｂ。真空紫外光谱表明：随着Ｇｄ３＋含量的增加，在１９２ｕｍ附近，出现了Ｇｄ＋的激发峰，且此峰的强度随着Ｇｄ３＋含量的增加而增大；同时位于１５０～１８５ｎｍ之间的基质吸收带的强度也增大；而位于２００～３００ｎｍ之间的Ｅｕ的电行迁移带的强度却随着Ｇｄ３＋含量的增加而降低。

La_2C~n(n=-1,0,+1)团簇的理论研究

用B3LYP/Lan1 2dz方法优化了La2 Cn(n =- 1 ,0 ,+1 )分子的结构 ,计算了La2 C的电子亲和势和离化能 ,并对计算结果进行了讨论。

Hydrothermal synthesis of the two-dimensional coordination polymer {[Fe(phen)(OH)](bta)(0.5)}(n) (phen=1,10-phenanthroline, bta=benzene-1,2,4,5-tetracaboxylate)

The title two-dimensional coordination polymer was synthesised and characterised by X-ray diffraction analysis.

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

LaC_4~n(n=-2,-1,0,+1,+2)分子簇的结构与稳定性

本文用密度泛函方法研究了LaC4n(n=-2,-1,0,+1,+2)分子簇的结构与稳定性。振动频率分析表明，在所提出的九个构型中，当ｎ＝-2，0，+1，+2时，稀土位于碳环上最稳定，而当ｎ＝-1时，尽管稀土位于碳环上能量最低，但没有找到稳定的构型，我们的结果还指出，稀土元素是分子簇中对外部环境最敏感的部位，即最具有反应活性

(Ce_(0.8)RE_(0.2))_(1-x)M_xO_(2-δ)固体电解质的溶胶-凝胶合成及其电性质

利用溶胶 凝胶法合成了 (Ce0 .8RE0 .2 ) 1-xMxO2 -δ(RE :稀土 ,M :碱土 )系列固体电解质 ,XRD表明 80 0℃即形成萤石结构 ,较高温固相反应合成温度低约 70 0℃ .测定了样品的电导率和阻抗谱 .XPS测试表明 ,掺杂碱土氧化物后吸附氧浓度明显增大 ,氧空位增多 ,电导率和氧离子迁移数增大 ,改善了CeO2 基固体电解质的性能 .讨论了碱土及稀土离子对电性质的影响 .(Ce0 .8Sm0 .2 ) 1-0 .0 5 Ca0 .0 5 O2 -δ80 0℃时电导率0 1 2 6S·cm-1,氧离子迁移数 0 .99.

Investigation of Pr valence and relationship between bond covalency and T-c in Y1-xPrxBa2Cu3O7 (x = 0-1)

The valence of Pr and relationship between bond covalency and T-c in Y1-xPrxBa2Cu3O7 (x = 0-1) have been studied using complex chemical bond theory. The results indicate that the depression of superconductivity in Y1-xPrxBa2Cu3O7 can be reasonably explained by bond covalency difference for the bonds between CuO2 plane and CuO chain. T-c decreases with the decreasing of bond covalency difference and reaches zero when bond covalency difference is zero (or bond covalency in CuO2 exceeds that in CuO chain) at Pr concentration 0.55 and valence +3.30. These are in good agreement with the experiments and meanwhile suggest that the valence of Pr is + 3.30 in Y1-xPrxBa2Cu3O7. The results also indicate that for Pr valence less than +3.15, superconductivity always exists for whatever Pr concentration, whereas for Pr with a valence of +4.0, superconductivity disappears as soon as Pr concentration exceeds 0.19. This supports with the viewpoint that higher valence Pr will contribute more electrons to CuO2 plane, filling the mobile holes responsible for conduction. For PrBa2Cu3O7 with no Ba-site Pr, our calculation suggests that it will be a superconductor if the average valence of Pr is less than +3.15. (C) 1998 Published by Elsevier Science B.V. All rights reserved.

Dependence of superconducting temperature on chemical bond parameters in YBa2Cu3O6+delta (delta=0-1)

The chemical bond parameters, that is ionicities and average energy gaps, for all types of chemical bonds in YBa2Cu3O6+delta have been investigated with variation of oxygen content delta (delta = 0.0, 0.35, 0.45, 0.58, 0.64, 0.73, 0.78, 0.81, 0.95, 1.00). The theory used is the complex crystal chemical bond theory, which is the development of P-V-L theory. The two plateaus near 90 K and 60 K in superconducting transition temperatures, and the disappearance of superconductivity with the change of oxygen content, were reasonably explained by chemical bond parameters. The results also showed that the Cu-O chains play a vital role in the transition from non-superconductors to superconductors, and the highest transition temperature occurred when the plane-chain reached a coupling state. (C) 1998 Elsevier Science Ltd. All rights reserved.

Theoretical investigation of LaC3n+ (n = 0, 1, 2) clusters by density functional theory

LaC3n+ (n = 0, 1, 2) clusters have been studied using B3LYP (Becke 3-parameter-Lee-Yang-Parr) density functional method. The basis set is Dunning/ Huzinaga valence double zeta for carbon and [2s2p2d] for lanthanum, denoted LANL1DZ. Four isomers are presented for each cluster; two of them are edge binding isomers with C-2 upsilon symmetry, the other two are Linear chains with C-infinity upsilon symmetry. Meanwhile, two spin states for each isomer, that is, singlet and triplet for LaC3+, doublet and quartet for LaC3 and LaC32+, respectively, are also considered. Geometries, vibrational frequencies, infrared intensities, and other quantities are reported and discussed. The results indicate that at some spin states; the C-2 upsilon symmetry isomers are the dominant structures, while for the other spin states, linear isomers are energetically favored. (C) 1998 John Wiley & Sons, Inc.

BaCe_(1-x)RE_xO_(3-0.5x)的溶胶 - 凝胶法合成及离子导电性

用溶胶－凝胶法合成了系列钙钛矿结构的ＢａＣｅ１－ｘＲＥｘＯ３－０．５ｘ（ＲＥ＝Ｌａ，Ｎｄ，Ｓｍ，Ｅｕ，Ｇｄ，Ｄｙ，Ｈｏ，Ｅｒ和Ｙ）复合氧化物，通过ＸＲＤ和热分析对样品结构及生成过程进行了研究．测定了不同温度下样品的交流阻抗谱，讨论了稀土离子掺杂对ＢａＣｅＯ３电性质的影响．溶胶－凝胶法比固相反应法合成温度降低了６００～８００℃，稀土掺杂使ＢａＣｅＯ３离子导电率提高了１０～４０倍.

Structure, Stability and Vibrational Spectra of LaC_5~n(n=-1,0,+1) Clusters

用密度泛含方法研究了ＬａＣ５ｎ（ｎ＝－１，０，＋１）分子簇的结构和稳定性及振动光谱，对这个六原子体系提出了三种可能构型，点群结构为Ｃ２ｖ对称性．第一个构型为Ｌａ接在弯曲的Ｃ５链上，第二个是Ｌａ通过二个键与Ｃ５环相连第三个是Ｌａ通过一个键与Ｃ５环相连；结果表明，第一个构型即当Ｌａ接在弯曲的Ｃ５链上时能量最低．振动光谱分析指出，当ｎ＝－１时，第二个构型为局域极小值；当ｎ＝＋１时，第一个和第二个构型为局域极小值；对ｎ＝０，局域极小值没有找到.

Theoretical Investigation of LaC~n and La_2C~n(n=-1,0,+1)Clusters

用密度泛函方法研究了ＬａＣｎ及Ｌａ２Ｃｎ（ｎ＝－１，０，＋１）分子簇的结构和稳定性．对Ｌａ２Ｃｎ体系，提出了两种可能构型，其中一种具有Ｃ２ｖ对称性，另一种具有Ｄ∞ｈ对称性．计算结果表明，对Ｌａ２Ｃｎ，当ｎ＝＋１，－１时，线状结构最稳定，并且在ｎ＝＋１时，Ｃ２ｖ结构极不稳定有收敛向线状结构的趋势．而当ｎ＝０时，Ｃ２ｖ结构最稳定．最后还计算了ＬａＣ和Ｌａ２Ｃ分子簇的电子亲和势和离化能.