Complex lanthanide chromate(VI)-phosphates K2R(CrO4)(PO4) (R = Dy-Lu, Y)

The conditions of formation of complex lanthanide chromate(VI)-phosphates K₂R(CrO₄)(PO₄) were found and these compounds were synthesized by solid-state synthesis with variation of the starting compounds, the temperature of synthesis (500–800 °C), and the annealing time (6–200 h). These salts are typical of late lanthanides, R = Dy-Lu, Y. Using lutetium derivatives as examples, it was shown that no similar compounds with lithium or sodium are formed. All the complex chromate(VI)-phosphates obtained decompose under static conditions at temperatures above 550 °C. They are isostructural and crystallize in the monoclinic system. The unit cell parameters for thulium, ytterbium, and lutetium compounds were calculated. It is shown by IR spectroscopy that PO₄ tetrahedra in the crystal lattice of potassium lanthanide chromate(VI)-phosphates are substantially distorted, whereas the CrO₄ tetrahedra retain the regular tetrahedron symmetry (T _d ). Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 622–626, April, 2006.     

Dy3+在Ba3La(BO3)3 中的光致发光

研究了Ba3La(BO3)3 基质中Dy3 的光致发光特性; 探讨了RE3 的电荷半径比(z/r)和Ce3 , Dy3 含量对Dy3 发光强度及发光颜色的影响; 分析了Ba3La(BO3)3 中Ce3 对Dy3 发光的敏化作用; 确定了Dy3 的 4F9/2→6H15/2及4F9/2→6H13/2跃迁发射的浓度猝灭机制均为电偶极-电四极相互作用.     

Synthesis and Crystal Structur of (4,4''-H2bipy)[CdBr4]·H2O

The title compound (4,4'-H2bipy)[CdBr4]·H2O 1 has been synthesized via hydrothermal reaction and characterized by X-ray diffraction. The crystal belongs to monoelinic,space group P21/c with a=8.260(3), b=23.926(7), c=9.774(2) (A), β=106.777(9)°,C10H12Br4CdN2O, Mr=608.26, V=1849.4(9)(A)3, Z=4, Dc=2.185 g/cm3, S=1.005, μ(MoKα)=9.814 mm-1, F(000)=1128, R=0.0646 and wR=0.0989. The crystal structure analysis of 1reveals that the title compound features an isolated structure, based on discrete 4,4'-H2bipy moieties and lattice water molecules which are linked by hydrogen bonds together with tetrahedral cadmium atoms terminally coordinated by four bromine atoms.     

Phase-fixed double-group 3-Γ symbols. IV. Real 3-Γ symbols and coupling coefficients for the group hierarchies T* ⊃ C 3 * and T* ⊃ C 2 *

We present sets of real 3- symbols which correspond to explicitly given irreducible matrix representations for the two double group hierarchies T* C ₃ ^* and T* C ₂ ^* . They fit into the formalism exposed in a previous paper [1] on the general theory of 3- symbols and coupling coefficients and illustrate much of the discussion in a subsequent one [2] treating the particular properties of the double groups.     

Synthesis and structures of new compounds based on tetrahedral rhenium chalcocyanide cluster anions [Re4Q4(CN)12]4− (Q = S or Se) and [Cu(bipy)2]2+ cations

The reactions of the rhenium chalcocyanide cluster salts K₄[Re₄Q₄(CN)₁₂]·6H₂O (Q = S or Se) with Cu²⁺ cations coordinated by the bidentate ligand 2,2′-bipyridyl (bipy) produced two new cluster compounds, [Cu(NH₃)(bipy)₂]₂[Re₄S₄(CN)₁₂]·bipy·3.25H₂O (1) and [{Cu(bipy)₂}₂Re₄Se₄(CN)₁₂]·bipy·8.5H₂O (2). The structures of these complexes were solved by X-ray diffraction. Compound 1 is ionic. Compound 2 is molecular. In the structures of both compounds, there are staking interactions between the {Cu(bipy)₂}²⁺ cationic moieties and the solvate 2,2′-bipyridyl molecules. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 1875–1878, November, 2006.     

Gas Hydrate Frameworks of Allen's Polyhedra. 2. Frameworks on 3–6 and 3–5–6 Nets

The structure of two classes of water molecule frameworks built up of 5¹²(D), 5¹²6²(T), 5¹²6³(P), and 5¹²6⁴(H) polyhedra is discussed. Polyhedral layers can be distinguished in the frameworks. The centers of the polyhedra belonging to a layer are at the nodes of planar networks consisting of triangular, pentagonal, and hexagonal meshes. The structure of one network determines exclusively the topology of the entire framework. Frameworks on 3–6 nets can be constructed of two types of polyhedral blocks: D₃T₂P₂and D₂T₆. Frameworks on 3–5–6 nets might include both specific blocks and the blocks involved in the frameworks on 3–5 and 3–6 nets. The paper analyzes the structure of frameworks on the nets built as a series of rows, each of these rows being constructed of pentagons or hexagons exclusively. These frameworks are described by the formula (D₃T₂P₂) _x (D₄H₂) _y (D₂T₆) _z , where x 1, y 0, and z 0 (x, y, and z are integers). Since all known frameworks of Allen's polyhedra satisfy this formula, they can be constructed of fragments of gas hydrate lattices with the CS1, CS2, and HS1 structures because they are derivatives of these key structures. Similar frameworks can be constructed of other tetrahedral particles (C, Si, SiO₂, etc.).     

A coupled electron diffraction and rigid unit mode (RUM) study of the crystal chemistry of some zeotypic AlPO4 compounds

Electron diffraction and lattice dynamical calculations are used to investigate the unit cells, space group symmetries and inherent displacive flexibility of the room-temperature average structures of AlPO₄-8, AlPO₄-16 and AlPO₄-tridymite. The zero-frequency rigid unit modes (RUMs) of the idealized high-symmetry polymorphs thereof are also investigated along with their relationship to the lower-temperature polymorphism of these zeotypic aluminophosphates. The clear presence of satellite reflections in addition to the Bragg reflections (G) of the underlying Cmc2₁ parent structure in the case of AlPO₄-8 shows that the true unit cell of the room-temperature polymorph has a doubled c-axis due to a condensed RUM mode. Structured diffuse scattering is also observed which can be related to the thermal excitation of RUM modes. In the case of AlPO₄-tridymite, a complex F1 triclinic polymorph is observed and related to soft RUM modes while, in the case of AlPO₄-16, a soft q=0 RUM mode is shown to be responsible for an observed phase transition in the case of the all SiO₂ analogue of AlPO₄-16. A large number of additional zero-frequency RUM modes also exist in the case of AlPO₄-16.     

“多角度欣赏面心立方晶胞”教学设计*

尝试利用“火花学院”App等在线交互资源,引导学生从立体几何及密置层堆积模型视角,观察、描述、绘制面心立方晶胞的正四面体填隙、正八面体填隙、三视图和沿体对角线投影图像,加深学生对以面心立方晶胞结构为基础的CaF₂→金刚石晶胞、NaCl→钙钛矿晶胞结构的理解;再结合新型材料透明镁铝尖晶石晶体结构的探讨,了解晶体制备中的掺杂改性等常用方法,发展学生的微观探析能力和科学创新意识。     

Effects of BaCu（B2O5 ） addition on sintering temperature and microwave dielectric properties of Ba5Nb4O15–BaWO4 ceramics

The effects of BaCu(B2O5)(BCB) addition on the microstructure, phase formation, and microwave dielectric properties of Ba5Nb4O15–BaWO4ceramic are investigated. As a sintering aid, BaCu(B2O5) ceramic could effectively lower the sintering temperature of Ba5Nb4O15–BaWO4ceramic from 1100?C to 950?C due to the liquid-phase effect. Meanwhile,BaCu(B2O5) addition effectively improves the densification of Ba5Nb4O15–BaWO4ceramic and significantly influences the microwave dielectric properties. X-ray diffraction analysis reveals that Ba5Nb4O15and BaWO4coexist with no crystal phase of BaCu(B2O5) in the sintered ceramics. The Ba5Nb4O15–BaWO4ceramics with 1.0 wt% BaCu(B2O5) sintered at 950?C for 2 h presents good microwave dielectric properties of εr = 19.0, high Q × f of 33802 GHz and low τfof2.5 ppm/?C.