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1.
A new solid solution of the quasi-one-dimensional composite crystal, , has been synthesized under of O2 at 830°C. The non-doped compound Ca0.83CuO2 consists of two interpenetrating monoclinic subsystems of the [Ca] atoms and the edge-shared square planar [CuO2] chains. Upon increasing x, both the subsystems undergo a phase change from monoclinic to orthorhombic (M-O). The M-O change occurs at x∼0.04 for the [(Cu,Co)O2] subsystem, while such a change occurs at x∼0.17 for the [Ca] subsystem. Magnetic susceptibility measurements show an evolution from a short-range ordered state near x=0 to a long-range antiferromagnetic state for the samples with x?0.15. The effective magnetic moment μeff is found to increase with increasing x from for x=0.10 to for x=0.30, suggesting that the solid solution can be regarded as Ca0.83[Cu0.662+Cu0.34−x3+Cox3+]O2, in which a mixed state of Cu2+(S=1/2), Cu3+(S=0) and high-spin Co3+(S=2) ions is realized.  相似文献   

2.
This contributions shows with a series of ab initio MP2 and DFT (BP86 and B3-LYP) computations with large basis sets up to cc-pVQZ quality that the literature value of the standard enthalpy of depolymerization of Sb4F20(g) to give SbF5(g) (+18.5 kJ mol−1) [J. Fawcett, J.H. Holloway, R.D. Peacock, D.R. Russell, J. Fluorine Chem. 20 (1982) 9] is by about 50 kJ mol−1 in error and that the correct value of (Sb4F20(g)) is +68 ± 10 kJ mol−1. We assign , , and values for SbnF5n with n = 2-4 and compare the results to available experimental gas phase data. Especially the MP2/TZVPP values obtained in an indirect procedure that rely on isodesmic reactions or the highly accurate compound methods G2 and CBS-Q are in excellent agreement with the experimental data, and reproduce also the fine experimental details at temperatures of 423 and 498 K. With these data and the additional calculation of [SbnF5n+1] (n = 1-4), we then assessed the fluoride ion affinities (FIAs) of SbnF5n(g), nSbF5(g), nSbF5(l) and the standard enthalpies of formation of SbnF5n(g) and [SbnF5n+1](g): FIA(SbnF5n(g)) = 514 (n = 1), 559 (n = 2), 572 (n = 3) and 580 (n = 4) kJ mol−1; FIA(nSbF5(g)) = 667 (n = 2), 767 (n = 3) and 855 (n = 4) kJ mol−1; FIA(nSbF5(l)) = 434 (n = 1), 506 (n = 2), 528 (n = 3) and 534 (n = 4) kJ mol−1. Error bars are approximately ±10 kJ mol−1. Also the related Gibbs energies were derived. ΔfH°([SbnF5n+1](g)) = −2064 ± 18 (n = 1), −3516 ± 25 (n = 2), −4919 ± 31 (n = 3) and −6305 ± 36 (n = 4) kJ mol−1.  相似文献   

3.
The two non-isotypical rubidium rare-earth(III) thiophosphates Rb3M3[PS4]4 of praseodymium and erbium can easily be obtained by the stoichiometric reaction of the respective rare-earth metal, red phosphorus and sulfur with an excess of rubidium bromide (RbBr) as flux and rubidium source at 950°C for 14 days in evacuated silica tubes. The pale green platelet-shaped single crystals of Rb3Pr3[PS4]4 as well as the pink rods of Rb3Er3[PS4]4 are moisture sensitive. Rb3Pr3[PS4]4 crystallizes triclinically in the space group (, , , α=84.329(4)°, β=88.008(4)°, γ=80.704(4)°; Z=2), Rb3Er3[PS4]4 monoclinically in the space group P21/n (, , , β=95.601(6)°; Z=4). In both structures, there are three crystallographically different rare-earth cations present. (M1)3+ is eightfold coordinated in the shape of a square antiprism, (M2)3+ and (M3)3+ are both surrounded by eight sulfur atoms as bicapped trigonal prisms each with a coordination number of eight as well as for the praseodymium, but better described as CN=7+1 in the case of the erbium compound. These [MS8]13− polyhedra form a layer according to by sharing edges with the isolated [PS4]3− tetrahedra (d(P-S)=200-209 pm, ?(S-P-S)=102-116°). These layers are stacked with a repetition period of three in the case of the praseodymium compound, but of only two for the erbium analog. The rubidium cation (Rb1)+ is located in cavities of these layers and tenfold coordinated in the shape of a tetracapped trigonal antiprism. The also tenfold but more irregularly coordinated rubidium cations (Rb2)+ and (Rb3)+ reside between the layers.  相似文献   

4.
Two zinc phosphates (ZnPO), [H2(N2C9H20)]·[Zn(H2PO4)4] (I) and [H2(N2C9H20)]2·[Zn2(HPO4)3(H2PO4)2]·H2O (II), are synthesized under hydrothermal conditions using 4-amino-2.2.6.6-tetramethylpiperidine as organic template. I crystallizes in space group with , , , α=92.57(1)°, β=89.76(1)°, γ=102.16(2)°, and Z=2. Its structure, refined to R=0.029 and Rw=0.076 for 4279 independent reflections, consists of [Zn(H2PO4)4]2− clusters held together through strong hydrogen bonds to form pseudo-layers between which the doubly protonated amine molecules are inserted. II is monoclinic, C2, with , , , β=103.72(5)°, and Z=4 (R=0.079, Rw=0.268, 2477 independent reflections). The structure of II consists of [Zn2(HPO4)3(H2PO4)2]4− inorganic (2D) layers built up from vertex-sharing [ZnO4] and [(H2/H)PO4] tetrahedra. Organic cations and water molecules ensure the connection between these layers via hydrogen bonds. It is shown that numerous (1D), (2D), e.g., [H2(N2C9H20)]2·[Zn2(HPO4)3(H2PO4)2]·H2O, and (3D) (ZnPO) result from the condensation of the [Zn(H2PO4)4]2− clusters.  相似文献   

5.
Single-phase 1:2 B-site ordered perovskites are formed in the (1−x)A2+(Li1/4Nb3/4)O3-(x)A2+(Li2/5W3/5)O3 systems, A2+=Sr and Ca, within the range 0.238?x?0.333. The X-ray and electron diffraction patterns are consistent with a P21/c monoclinic supercell, , , , β≈125°, where the 1:2 order is combined with bbc+ octahedral tilting. Rietveld refinements of the ordered A(BI1/3BII2/3)O3 structures give a good fit to a model with BI occupied by Li and Nb, BII by W and Nb, and a general stoichiometry (Sr,Ca)(Li3/4+y/2Nb1/4−y/2)1/3(Nb1−yWy)2/3O3, y=0.9x=0.21-0.30. The Sr system also includes regions of stability of a 1:3 ordered phase for 0.0?x?0.111, and a 1:1 ordered double perovskite for 0.833?x?1.0. The formation of the non-stoichiometric 1:2 ordered phases is associated with the large site charge/size differences that can be accessed in these systems, and restricted by local charge imbalances at the A-sites for W-rich compositions. These concepts are used to generate stability maps to rationalize the formation of the known 1:2 ordered oxide perovskites.  相似文献   

6.
Layered compounds with the general formula MOXO4·yH2O (M=V, Nb; X=P, As) were prepared. The content of water y was controlled by keeping the samples in an atmosphere with various relative humidities (RH). Depending on RH, the formation of several hydrates of niobyl phosphate and arsenate was observed and their basal spacings (d) were determined, namely, NbOPO4·H2O, , at 11% RH and lower, NbOPO4·2H2O, , at 22-33% RH, NbOPO4·3H2O, , at 43-84% RH, and NbOPO4·5H2O, , at 92% RH and above; NbOAsO4·H2O, , at 0-16% RH and NbOAsO4·3H2O, at 33% RH and above. As follows from ac and dc conductivity data, NbOXO4·yH2O compounds are practically pure protonic conductors, whereas VOXO4·yH2O compounds are mixed protonic-electronic conductors and the protonic component increases with y. Two intercalates of MOXO4·yH2O with inorganic acids were prepared. A new intercalate of H3AsO4 into VOAsO4·yH2O with the formula VOAsO4·0.5H3AsO4·yH2O (y=0.5-0.8) has the cell parameters a=6.37 and at 0-22% RH. Above 22% RH, the intercalate decomposes and the parent VOAsO4·yH2O with H3AsO4 adsorbed on the surface is formed. Another intercalate with formula NbOPO4·H3PO4·yH2O (y=2-4 at 0-75% RH) has the cell parameters a=6.43 and at RH from 0% to 5% and a=6.48 and at RH from 33% to 75%. Both intercalates are more conductive than their MOXO4·yH2O hosts and their conductivity increases with increasing RH of the surrounding atmosphere. Like NbOPO4·yH2O, also NbOPO4·H3PO4·yH2O can be considered pure proton conductor and its conductivity at 20 °C reaches 5×10−3 S cm−1 for y=4.  相似文献   

7.
Although both end members in the (1−x)Ba(Li1/4Nb3/4)O3-xBa(Li2/5W3/5)O3 (BLNW) system adopt a hexagonal perovskite structure, B-site ordered cubic perovskites are formed for the majority of their solid solutions (0.238?x?0.833). Within this range, single-phase 1:2 order (, , ) is stabilized for 0.238?x?0.385. In contrast to all known A(B1/3IB2/3II)O3 perovskites, the 1:2 ordered BLNW solid solutions do not include any composition with a 1:2 cation distribution and the structure exhibits extensive non-stoichiometry. Structure refinements support a model where Li and W occupy different positions and Nb is distributed on both sites, i.e. Ba[(Li3/4+y/2Nb1/4−y/2)1/3(Nb1−yWy)2/3]O3 (y=0.21-0.35, where y=0.9x). The stabilization of the non-stoichiometric order arises from the large charge/size site differences; the loss of 1:2 order for W-rich compositions is related to local charge imbalances on the A-site sub-lattice. The range of single-phase 1:1 order is confined to x=0.833, (Ba(Li3/4Nb1/4)1/2(W)1/2)O3), where the site charge/size difference is maximized and the on-site mismatches are minimized. The microwave dielectric loss properties of the ordered BLNW solid solutions are significantly inferior as compared to their stoichiometric counterparts.  相似文献   

8.
The single crystals of lanthanum metaphosphate MLa(PO3)4 (M=Na, Ag) have been synthesized and studied by a combination of X-ray crystal diffraction and vibrational spectroscopy. The sodium and silver compounds crystallize in the same monoclinic P21/n space group ( factor group) with the following respective unit cell dimensions: a=7.255(2), b=13.186(3), , β=90.40(2)°, , Z=4 and a=7.300(5), b=13.211(9), , β=90.47(4)°, , Z=4. This three-dimensional framework is built of twisted zig-zag chains running along a direction and made up of PO4 tetrahedra sharing two corners, connected to the LaO8 and NaO7 or AgO7 polyhedra by common oxygen atoms to the chains. The infrared and Raman vibrational spectra have been investigated. A group factor analysis leads to the determination of internal modes of (PO3) anion in the phosphate chain.  相似文献   

9.
Tetrahydroborate enclathrated sodalites with gallosilicate and aluminogermanate host framework were synthesized under mild hydrothermal conditions and characterized by X-ray powder diffraction and IR spectroscopy. Crystal structures were refined in the space group P-43n from X-ray powder data using the Rietveld method. Na8[GaSiO4]6(BH4)2: a=895.90(1) pm, V=0.71909(3)×10−6 nm3, RP=0.074, RB=0.022, Na8[AlGeO4]6(BH4)2: a=905.89(2) pm, V=0.74340(6)×10−6 nm3, RP=0.082, RB=0.026. The tetrahedral framework T-atoms are completely ordered in each case and the boron atoms are located at the centre of the sodalite cages. The hydrogen atoms of the enclathrated anions were refined on x, x, x positions, restraining them to boron-hydrogen distances of 116.8 pm as found in NaBD4.The IR-absorption spectra of the novel phases show the typical bands of the tetrahedral group as found in the spectrum of pure sodium boron hydride.The new sodalites are discussed as interesting -containing model compounds which could release pure hydrogen.  相似文献   

10.
11.
The chloride derivatized lanthanoid(III) cyclo-tetrasilicates of the composition M6Cl10[Si4O12] (M=Sm, Gd-Dy) crystallize monoclinically in space group C2/m (a=1062-1065, b=1036-1052, c=1163-1187 pm, β≈103°, Z=2). They are obtained by the reaction of the sesquioxides M2O3 (or the combination of Tb4O7 and Tb in 3:2-molar ratio for the terbium case), the corresponding trichlorides MCl3, and SiO2 (silica gel) in stoichiometric ratios with double the amount of MCl3 as flux in evacuated silica tubes (7d at 850 °C) as transparent, pseudo-octagonal, pillar-shaped single crystals with the colour of the respective lanthanoid trication M3+. Their crystal structure can be considered as a layered arrangement in which cationic {[(M2)5Cl9]6+} layers are alternatingly piled with anionic ones of the kind {[(M1)Cl[Si4O12]]6−}. In the latter, the (M1)3+ cations show a slightly distorted hexagonal bipyramidal environment built up by two Cl and six O2− anions (CN=8), whereas the (M2)3+ cations exhibit a coordination number of only seven (five Cl and two O2− anions in the shape of a distorted pentagonal bipyramid). The cyclo-tetrasilicate units consist of four corner-linked [SiO4]4− tetrahedra in all-ecliptical conformation each, fused to eight-membered rings, which contain two almost linear (178°) and two bent (142°) Si-O-Si bridges. This particular cyclo-[Si4O12]8− situation could be confirmed by theoretical and experimental infrared-spectroscopic investigations.  相似文献   

12.
13.
Two new open-framework zinc phosphites, [M(C6N4H18)][Zn3(HPO3)4] (M=Ni, Co), have been prepared under hydrothermal conditions. Single-crystal X-ray diffraction analysis shows that [Ni(C6N4H18)][Zn3(HPO3)4] (1) and [Co(C6N4H18)][Zn3(HPO3)4] (2) are isostructural and both crystallize in the monoclinic space group C2/c with , , , β=109.83(3)°, Z=4, R1=0.0408 (I>2σ(I)), and wR2=0.1104 (all data) for 1, and , , , β=109.328(2)°, Z=4, R1=0.0380 (I>2σ(I)), and wR2=0.1093 (all data) for 2. The structures of 1 and 2 are built up from strictly alternating ZnO4 tetrahedra and HPO3 pseudo-pyramids linked through oxygen vertices to form the three-dimensional (3-D) open-frameworks with multi-directional intersecting 12-membered ring (12-MR) channels. The M(TETA) (M=Ni, Co) complexes self-assembled under hydrothermal system connect with the inorganic host via M-O-P linkages and interact with inorganic framework through weak H-bonds. The two compounds show intense photoluminescence upon photoexcitation at 235 nm.  相似文献   

14.
15.
The crystal structure of WOCl3, determined on the basis of powder diffraction data (tetragonal, P42/mnm, a=10.6856(6), c=3.8537(2)), is isotypic to WOI3 and contains one-dimensional strands of edge-sharing double-octahedral W2O4/2Cl6 groups connected via common corners in trans position. A W-W bond of 2.99 Å is present within the planar W2Cl6 groups. A series of non-stochiometric, mixed valence W(IV,V) compounds M1−x[W2O2Cl6] can be obtained from WOCl3 by reaction with metal halides (TlCl, KCl, PbCl2) or by reaction of elemental Hg with WOCl4. All were characterized by single crystal structure determinations and EDX measurements (Tl0.981(2)[W2O2Cl6]: monoclinic, C2/m, a=12.7050(4), b=3.7797(1), , β=107.656(1)°; K0.84(2)[W2O2Cl6]: monoclinic, C2/m, a=12.812(3), b=3.7779(6), , β=107.422(8)°; Pb0.549(3)[W2O2Cl6]: orthorhombic, Immm,a=3.7659(1), b=9.8975(4), ; Hg0.554(6)[W2O2Cl6]: monoclinic, C2/m, a=12.8361(8), b=3.7622(3), , β=113.645(3)°). Two representatives of this family of compounds have already been reported: Na[W2O2Br6] [Y.-Q. Zhang, K. Peters, H.G. von Schnering, Z. Anorg. Allg. Chem. 624 (1998) 1415-1418] and Ag0.74[W2O2Br6] [S. Imhaïne, C. Perrin, M. Sergent, Mat. Res. Bull. 33 (1998) 927-933]. The Ag containing compound can be obtained from elemental Ag and WOBr3. The crystal structure, originally reported in the triclinic system, was redetermined and shown to be monoclinic with space group C2/m (a=13.7338(10), b=3.7769(3), , β=112.401(3)°). The crystal structures of these compounds are in close relationship to the structure of WOCl3 and all contain W2O4/2X6 (X=Cl, Br) double strands with the mono and divalent cations coordinated by the terminal halogen atoms of the W2X6 groups and a short W-W bond (2.85 Å for X=Cl). A cube-shaped coordination environment is present for M=Tl, K and a trigonal-prismatic coordination for M=Ag, Hg. Hg0.55[W2O2Cl6] is a semiconductor with a non-Arrhenius behaviour, high specific conductivity of 0.05 Ω-1 cm−1 and a very small activation energy of 0.03 eV. Hg0.55[W2O2Cl6] and Ag0.8[W2O2Br6] show a temperature independent paramagnetism with a magnetic moment around 300×10-6 cm3 mol-1.  相似文献   

16.
Two rare-earth compounds containing selenium atoms, La(HSeO3)(SeO4) with a new open framework structure and KNd(SeO4)2 with a layered structure, have been synthesized under “sol-gel” hydrothermal conditions for the first time. Single-crystals of La(HSeO3)(SeO4) crystallize in the monoclinic system (P21, , , , β=104.91(3)°, Z=2, RAll=0.032). The structure contains puckered polyhedral layers made of LaOx (x=9,10) and SeO4 groups, which are connected via SeO3-uints to the 3D structure. The crytal structure of KNd(SeO4)2 (monoclinc, P21/c, , , , β=91.38(3)°, Z=4, RAll=0.051) contains honeycomb-like six-ring NdO9 polyhedra forming layers which are further decorated with SeO4 tetrahedra. The K+ ions occupy the interspaces of these layers and provide the charge balance.  相似文献   

17.
The reactions of UO3 and TeO3 with KCl, RbCl, or CsCl at 800 °C for 5 d yield single crystals of A2[(UO2)3(TeO3)2O2] (A=K (1), Rb (2), and Cs (3)). These compounds are isostructural with one another, and their structures consist of two-dimensional sheets arranged in a stair-like topology separated by alkali metal cations. These sheets are comprised of zigzagging uranium(VI) oxide chains bridged by corner-sharing trigonal pyramidal TeO32− anions. The chains are composed of dimeric, edge-sharing, pentagonal bipyramidal UO7 moieties joined by edge-sharing tetragonal bipyramidal UO6 units. The lone-pair of electrons from the TeO3 groups are oriented in opposite directions with respect to one another on each side of the sheets rendering each individual sheet non-polar. The alkali metal cations form contacts with nearby tellurite oxygen atoms as well as with oxygen atoms from the uranyl moieties. Crystallographic data (193 K, MoKα, ): 1, triclinic, space group , , , , α=101.852(1)°, β=102.974(1)°, γ=100.081(1)°, , Z=2, R(F)=2.70% for 98 parameters and 1697 reflections with I>2σ(I); 2, triclinic, space group , , , , α=105.590(2)°, β=101.760(2)°, γ=99.456(2)°, , Z=2, R(F)=2.36% for 98 parameters and 1817 reflections with I>2σ(I); 3, triclinic, space group , , , , α=109.301(1)°, β=100.573(1)°, γ=99.504(1)°, , Z=2, R(F)=2.61% for 98 parameters and 1965 reflections with I>2σ(I).  相似文献   

18.
The high temperature reaction of C60 with silver(I) trifluoroacetate followed by 500 °C sublimation and subsequent HPLC purification has led to the isolation of the five trifluoromethyl[60]fullerenes C60(CF3)n (n=2, 4, 6, 8, 10). Four of them have >90% compositional purity. Two of the compounds, C60(CF3)4 and C60(CF3)6, were obtained as C1-symmetry isomers with >90% isomeric purity, and a sample of C60(CF3)2 also contained ca. 15-20% of a Cs-symmetry isomer of C60(CF3)4. The new compounds were characterized by IR and EI mass spectrometry (all five compounds), NMR spectroscopy (C60(CF3)2, C60(CF3)4, and C60(CF3)6), and 2D COSY NMR spectroscopy (C60(CF3)4 and C60(CF3)6). Calculations at the AM1 and DFT levels of theory have led to the prediction of the most likely structures for C60(CF3)2, C1-C60(CF3)4, Cs-C60(CF3)4, and the two most likely structures of C1-C60(CF3)6.  相似文献   

19.
Crystal structure and phase transformations of calcium yttrium orthophosphate Ca3Y(PO4)3 were investigated by X-ray powder diffraction, selected-area electron diffraction, transmission electron microscopy and optical microscopy. The high-temperature phase is isostructural with eulytite, cubic (space group ) with a=0.983320(5) nm, V=0.950790(8) nm3, Z=4 and Dx=3.45 Mg m−3. The crystal structure was refined with a split-atom model, in which the oxygen atoms are distributed over two partially occupied sites. Below the stable temperature range of eulytite, the crystal underwent a martensitic transformation, which is accompanied by the formation of platelike surface reliefs. The inverted crystal is triclinic (space group P1) with a=1.5726(1) nm, b=0.84267(9) nm, c=0.81244(8) nm, α=109.739(4)°, β=90.119(5)°, γ=89.908(7)°, V=1.0134(1) nm3, Z=4 and Dx=3.24 Mg m−3. The crystal grains were composed of pseudo-merohedral twins. The adjacent twin domains were related by the pseudo-symmetry mirror planes parallel to with the composition surface . When the eulytite was cooled relatively slowly from the stable temperature range, the decomposition reaction of Ca3Y(PO4)3β-Ca3(PO4)2+YPO4 occurred.  相似文献   

20.
The bismuth basic nitrate [Bi6O4(OH)4](NO3)6 crystallizes in a rhombohedral hexagonal unit cell with parameters , , , Z=6, space group R-3. The synthesis, formula determination, thermogravimetric analysis and nitrate assay, and finally, its crystal structure refinement determined at 150(2) K by synchrotron X-ray microcrystal diffraction are reported. Its structure is built from [Bi6O4(OH)4]6+ polycations, six per unit cell, disordered over two positions. Two oxygen atoms are common to the two antagonist polycations (full occupancy) while the remaining six are partially occupied. The [Bi6O4(OH)4]6+ hexanuclear clusters form columns along the c-axis. The cohesion between polycationic entities is effected by nitrate anions through either OH-ONO2 hydrogen bonds or Bi-ONO2 bonds. One of the two independent [NO3] groups is also disordered over two positions. Only a local order in the columns is obtained by formation of pairs of ordered [Bi6O4(OH)4]6+ polycations.  相似文献   

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