Crystal growth and TG-DTA properties of K(2)Ln(NO3)(5).2H(2)O (Ln = La, Ce, Pr, Nd, Sm)

Single crystals of KLnN(Ln=La, Ce, Pr, Nd, Sm) can be grown in water solution with pH approximate to 1 similar to 2 at about 40 degrees C. Crystals of KLnN (Ln=La, Ce, Pr, Nd) are orthorhombic with space group Fdd2. KPrN crystal was grwon and its crystal structure was determined for the first time. The KPrN crystal parameters obtained by the direct method are as follows: a=21.411(3) Angstrom, b=11.2210(10)Angstrom, c=12.208(2) Angstrom, Z=6, R=0.0240. The TG-DTA curves of KLnN(Ln=La,Ce, Pr, Nd, Sm) demonstrate that the processes of dehydration, melt, irreversible phase transition and decomposition of NO3- take place in sequence with the temperature increasing(except KCN). There are three steps in the decomposition of NO3- in KLnN(Ln=La, Nd, Sm) while two steps in KLnN (Ln=Ce, Pr). K(2)Ln(NO3)(5). 2H(2)O are formed at about 225 degrees C by the reaction of the starting materials of KNO3 and Ln(NO3)(3). nH(2)O.

Calculation of nonlinear optical coefficients of orthorhombic Re-2(MoO4)(3) crystals

From the chemical bond viewpoint, the second-order nonlinear optical (NLO) tensor coefficients of some Re-2(MoO4)(3) (ReMO)-type tare earth molybdates, with Re = Pr, Nd, Sm, Eu, Gd, Tb and Dy, have been calculated by using the chemical bond theory of complex crystals and the modified bond charge model. All kinds of constituent chemical bonds are considered in the calculation. The major part of the NLO properties of these ReMO crystals is found from the ReO7 groups. The NLO coefficients of these ReMO crystals decrease with Re from Pr to Dy. (C) 1998 Elsevier Science Ltd. All rights reserved.

Synthesis and X-ray crystal structure of [(eta(5)-C5H5)Sm(mu-OC20H20N2O)](2)(mu-THF)(THF)(2): Mono(cyclopentadienyl)lanthanide complex bearing a C-2-symmetric tetradentate Schiff-base ligand

Cp2SmCl(THF) reacts with 0.5 equivalent disodium salts of trans-(+/-)-N,N'-bis(salicylidene)-1,2-cyclohexanediamine give the title complex [(eta(5)-C5H5)Sm(mu-OC20H20N2O)](2)(mu-THF)(THF)(2) (1). X-ray crystal determination shows that the molecule is a dimer, in which two (eta(5)C(5)H(5))Sm(mu-OC20H20N2O) units are connected via a THF oxygen and two bridging oxygen atoms of Schiff base ligands. The average Sm-C distance is 2.78(7) Angstrom, while those of Sm-O (bridging THF oxygen) and Schiff base oxygens are 2.79(3) and 2.43(4) Angstrom; respectively. (C) 1998 Elsevier Science Ltd. All rights reserved.

The bond ionicity in RBa2Cu3O7 (R=Pr, Sm, Eu, Gd, Dy, Y, Ho, Er, Tm)

RBa2Cu3O7 (R = Pr, Sm, Eu, Gd, Dy, Y, Ho, Er, Tm) has been studied using complex chemical bond theory. The results indicated that with the decreasing of R radius, the ionicities for all considered types of bond decrease. This is in good agreement with the experimental fact that T-c decreases with the decreasing of R radius. PrBa2Cu3O7 with no Ba-site Pr in this calculation is also predicted to be a superconductor. This supports the conclusion obtained by Blackstead et al. The ionicity for each bond obeys the following order: Ba-O > R-O > Cu(2)-O(1) > Cu(2)-O(2,3) > Cu(1)-O(4) similar to Cu(1)-O(1).

K_2Ln(NO_3)_5·2H_2O(Ln=La,Ce,Pr,Nd,Sm)的晶体生长和热重-差热分析研究

本文生长出了K2Ln（NO3）5.2H2O（Ln=La；Ce；Pr；Nd；Sm）的单晶，并对其进行了晶体结构及差热-热重分析研究．结果表明，K2Ln（NO3）5.2H2O（Ln=La；Ce；Pr；Nd）的晶体属正交晶系，Fdd2空间群．首次生长出KPrN单晶并用直接法解出其晶体结构．解得KPrN的晶胞参数为：a=11．2210（10）,b=21．411（3），c=12．208（2）,Z=6；R=0．0240．对KLnN加热，则依次出现脱水、熔化、不可逆相变和NO的分解过程（K2Ce（NO3）5·2H2O除外）K2Ln（NO3）5·2H2O（Ln＝La；Nd；Sm）的NO分三步分解，K2Ln（NO3）5·2H。O（Ln=Ce；Pr）的NO分两步分解·KNO3和Ln（NO3）3·nH2O的混合物在225℃左右生成K2Ln（NO3）5

非线性光学新材料K_2Ln(NO_3)_5.2H_2O(Ln=La,Ce,Pr,Nd,Sm)的晶体生长、结构和表征

非线性光学新材料Ｋ２Ｌｎ（ＮＯ３）５·２Ｈ２Ｏ（Ｌｎ＝Ｌａ，Ｃｅ，Ｐｒ，Ｎｄ，Ｓｍ）的晶体生长、结构和表征董文庭张洪杰苏锵（中国科学院长春应用化学研究所稀土化学与物理开放实验室，长春１３００２２）Ｇｒｏｗｔｈ，ＳｔｒｕｃｔｕｒｅａｎｄＣｈａｒａｃｔ...

PREPARATION STRUCTURE AND PHYSICAL-PROPERTIES OF NEW SILVER LANTHANIDE MOLYBDENUM OXIDES [AGLNMO(2)O(8)(LN=LA-ND AND SM)]

We present the synthesis of AgLnMo(2)O(8) compounds with Ln = La-Nd and Sm. These compounds represent a scheelite-type structure characterized by MoO4- tetrahedrons. IR spectra show five absorption peaks in the region of 1000-400cm(-1), around 800cm(-1) and 400cm(-1), which correspond to the modes of the tetrahedral MoO42- groups. All of AgLnMo(2)O(8) (Ln = La-Nd and Sm) oxides are dielectric materials at room temperature. The temperature dependence of the magnetic susceptibility ofAgLnMo(2)O(8) (Ln = Ce-Nd and Sm) shows Curie-Weiss law behavior from 100K to 300K. This indicates that both Ce and Pr exist in +3 oxidation state in AgLnMo(2)O(8). For AgLaMo2O8, diamagnetic properties are found as expected.

SEMICONDUCTOR TO METAL TRANSITION IN LN(2)MO(3)O(9) COMPOUNDS

Ln(2)Mo(3)O(12) and Ce2Mo3O12.25 are reduced by hydrogen yielding Mo4+ oxides of the formula Ln(2)Mo(3)O(9) (Ln = La, Ce, Pr, Nd, Sm, Gd and Dy). The new compound Ce2Mo3O9 has the same structure as other Ln(2)Mo(3)O(9) compounds. All of the products are single phase materials and crystallize in a tetragonal scheelite type structure with Mo2O6 clusters. The IR spectra of the Ln(2)Mo(3)O(9) oxides show two absorption bands. These compounds are black n-type semiconductors, and exhibit Curie-Weiss Law behavior from 100K to 250K. Temperature dependence of the electrical properties of these compounds were measured for the first time, and a semiconductor-metal transition was found at about 250 degrees C.

η~6—芳烃希土有机配合物的合成、结构及性能研究——Ⅰ.Sm(η~6—C_6H_6)(AlCl_4)_3的合成及晶体结构

经过铝粉加热活化的AlCl_3与SmCl_3在苯中反应,得到了Sm(η~6—C_6H_6)(AlCl_4)_3·C_6H_6单晶.其晶体属于三斜晶系,P1空间群,晶胞参数a=9.456(2)(?),b=9.765(3)(?),c=16.776(4)(?),α=96.00(2)°,β=93.76(2)°,γ=111.66(2)°,V=1422.55(?)~3,Z=2.晶体结构是采用Patterson和Fourier合成法解出的,所有非氢原子的坐标及各向异性热振动参数经块矩阵最小二乘法修正,最后偏离因子R=0.031,R_ω=0.035.分子结构中,中心离子Sm(Ⅲ)与六个Cl原子及一个苯环上的六个C原子成键.Sm-C键平均距离2.92(?),Sm-Cl平均距离2.83(?).与希土相连的六个Cl原子,其中之五构成平面五边形,整个分子呈大致的五角双锥形.

雅江点地梅（报春花科）3个居群的核型和倍性变化

首次报道了雅江点地梅(Androsace yargongensis) 3 个居群的染色体数目和核型, 对倍性也进行研究。3个居群的染色体数目(2n) , 核型公式(KF) , 染色体相对长度组成(C.RL ), 核型不对称系数(A s. K% ) 和核型类型(KT) 分别为: 野牛沟居群2n= 40; KF = 36 m(1SA T) + 2SM + 2ST + 2b, C. RL = 2L + 14M 2+ 22M 1+ 2S+ 2bS,As.K= 54. 75% , KT = 2A;巴颜喀拉山居群2n= 40, KF = 36 m + 2 sm + 2 st+ 1b, C.RL = 4L + 16M 2+ 18M 1+ 2S+1bS,As.K= 56. 31% , KT = 2B; 达坂山居群2n= 60, KF= 40 m + 14 sm + 6 st, C.RL = 4L +24M 2+ 26M 1+ 6S,As.K= 59. 56% , KT = 2B。根据3 个居群的染色体和核型不对称性与居群所在地的地理位置, 认为雅江点地梅核型和倍性的演化与高海拔生态环境和寒冷、干旱的气候加剧有密切关系。

矿物中REE扩散作用的理论研究——兼论白钨矿Sm-Nd定年方法的可靠性

元素在矿物中的扩散作用，对其在地质体中的配布有着重要影响，被越来越多的用来解决地球化学动力学方面的问题。稀土元素（REE）能反映重要的地球化学信息，作为地球化学的示踪剂被广泛应用于探讨各类岩石成因和矿床成因。因此，查明REE在矿物中的扩散行为对于地学研究具有重要意义。 前人对元素（如O、Ar等）在不同矿物中扩散行为的理论研究，大多采用的是矿物晶格单独制约扩散速率的模型，由于稀土元素的离子半径各不相同，用此类模型来探讨其在不同矿物中的扩散行为是不合适的。为了寻求获取矿物中稀土元素扩散参数的简捷途径，本博士论文通过对前人关于矿物中REE扩散作用研究的实验结果进行分析归纳，探讨了扩散体系不同因素对扩散行为的控制规律。在此基础上，使用多元统计分析方法建立了预测REE在不同矿物中扩散参数的多变量模型，由此模型计算的1atm、无水环境下REE的扩散参数与实验测定结果在实验误差范围内相当吻合。与前人的模型相比，多变量模型能更全面地反映扩散体系各因素对扩散速率的制约。 此外，为了检验白钨矿Sm-Nd同位素定年方法的可靠性，本论文从不同角度进行了研究： （一） 理论验证 矿物内部的微量元素信息能否有效保存，在很大程度上取决于其扩散速率，因此本文从扩散动力学角度对白钨矿Sm-Nd同位素体系的封闭性进行了探讨。通过理论计算并结合实验模拟验证的方式获得了白钨矿中Sm、Nd的扩散参数，得出在1atm、无水环境下Sm和Nd的扩散方程为： Nd：D＝4.00exp（－438kJmol-1/RT）cm2/s Sm：D＝1.85exp（－427kJmol-1/RT）cm2/s 借助这些扩散数据，对白钨矿中Sm-Nd信息受扩散作用的影响程度做了分析。结果表明，在大多数地质环境下，Sm、Nd在白钨矿晶体中的扩散速率很低，同位素体系容易保持封闭不受热力学作用的影响。 （二） 地质验证 以湘西沃溪Au-Sb-W矿床为研究对象，通过对不同矿体的白钨矿进行Sm-Nd同位素年龄测定，将其结果与其它同位素方法得到的年龄数据以及野外地质关系、区域构造演化等进行了对比。结果表明，沃溪Au-Sb-W矿床的白钨矿Sm-Nd年龄结果与Ar-Ar年龄是一致的，与野外地质关系及区域构造演化特征等也相当吻合。 通过本论文的工作，得出以下主要成果和认识： （1）首次建立了适合于计算REE在不同矿物中扩散参数的理论模型，为研究矿物中REE的扩散行为提供了可靠的理论方法。 （2）首次获得了白钨矿中Sm-Nd的扩散参数，探讨了白钨矿中REE的扩散性质，并建立了1atm、无水环境下Sm和Nd在此矿物中的扩散方程。 （3）通过扩散动力学研究，得出白钨矿中Sm-Nd同位素体系的封闭性较为理想，为评价Sm-Nd同位素方法是否适合于制约白钨矿的成矿年龄提供了理论依据。 （4）通过不同同位素定年结果的比较以及与野外地质关系、区域构造演化等的对比，得出白钨矿Sm-Nd同位素年龄结果是真实有效的，从矿床学角度为评价该同位素定年方法的可靠性提供了实践证据。