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1.
The crystal structure of Na7Mg4.5(P2O7)4 has been solved by direct methods from the three-dimensional X-ray data. The space group is . The crystal structure consists of Mg2+, Na+, and P2O4?7 ions. One magnesium atom at symmetry center (0,0,0) and two sodium atoms at ±(?0.0421, ?0.0596, 0.2230) display occupation factors 0.5 each. A short interatomic distance between these Na+ and Mg2+ ions (1.80 ± 0.01 Å) excludes the occupation of both sites in the same unit cell. The crystal structure of Na7Mg4.5(P2O7)4 consists of unit cells containing Na8Mg4(P2O7)4 or Na6Mg5(P2O7)4 with a statistical occurrence 1:1.Each Mg2+ ion is octahedrally coordinated by six O2? ions at distances 1.979 – 2.270 Å. The coordination polyhedra around the Na+ ions are ill-defined. The bond angles POP in the P2O4?7 groups are 126.6 and 133.6° (±0.3°). The final reliability factor R is 7.1%. 相似文献
2.
Nickel-ammonium tetrametaphosphate, Ni(NH4)2P4O12 · 7H2O is triclinic with a = 13.841(3); b = 9.621(5); c = 7.482(2)Å; α = 98.05(4); β = 97.25(4); γ = 103.01(4)°; M = 536.59; V = 947.9Å3; Z = 2; Dx = 1.879 g cm?3; μ = 14.524 cm?1, and space group . The crystal structure was solved using 1661 independent reflections measured on a single-crystal diffractometer (MoKα). The final R value is 0.056. The two crystallographic independent nickel atoms Ni(1) and Ni(2) are octahedrally coordinated: Ni(1) by four oxygen atoms and two water molecules, Ni(2) by six water molecules. Ni(1), closely connected to two P4O12 rings, forms a complex anion [Ni(P4O12)2(H2O)2]6? which is associated to ammonium polyhedra and [Ni(H2O)6]2+ octahedra. Another interesting feature of this atomic arrangement is the presence of a large channel (10 × 4) Å2 parallel to the axis. The internal surface of this channel is covered by six zeolitic water molecules. 相似文献
3.
The excitation-transfer reaction in thermal energy collisions of state-selected metastable Ar*(3P2) and Ar*(3P0) atoms with ground state H atoms, giving excited H*(n = 2) atoms, has been studied with the stationary afterglow technique. The rate constant for the excitation of H atoms by Ar*(3P2) has been found to be more than one order of magnitude larger than in excitation by Ar*(3P0). This difference in the reactivity of two metastable species is explained to be a consequence of the attractive nature of the D(2II) and E(2Σ+) potentials that develop from the Ar*(3P2)+H entrance channel and which give curve crossing with the B(2II) and C(2Σ+ potentials, respectively, leading to the Ar+H*(n=2) exit channel, whereas only a repulsive 4II (Ω=) potential develops from the Ar*(3P0+H entrance channel. 相似文献
4.
M. Gabelica-Robert M. Goreaud Ph. Labbe B. Raveau 《Journal of solid state chemistry》1982,45(3):389-395
The high-temperature form of NaFeP2O7 crystallizes in the monoclinic space group with a = 7.3244(13), b = 7.9045(7), c = 9.5745(15), Å, β = 111.858(13)°, and Z = 4. The structure has been refined from 3842 reflections leading to R = 0.040 and Rw = 0.047. The structure of II-NaFeP2O7 can be described by alternately stacking layers containing the FeO6 octahedra and layers formed by the P2O7 groups, parallel to (001). Elongated cages are formed where two Na+ ions are located. The structure is compared with that of KAlP2O7. Both structures are built up from blocks of three polyhedra, [FeP2O11] or [AlP2O11], including a small OoctOtetOoct angle. These blocks are connected in such a way that several types of tunnels appear in each structure. 相似文献
5.
Single crystal X-ray diffraction photographs taken with a Buerger precession camera, at temperatures 250, 214, and 122 K, corroborate the existence of three low-temperature phases of Ag26I18W4O16. These phases are labeled α′, β, and γ in order of decreasing temperature. The α′ phase is monoclinic, space group P21, Z = 2; the β phase is triclinic, space group or P1, Z = 2; and the γ phase is triclinic, space group P1, Z = 1. Lattice constants at the aforementioned temperatures are given. Twins in the β and γ phases are related by the albite and pericline laws, as are twins in the feldspars. The highest symmetry known to be attained by the (W4O16)8? entity is 2(C2), which, strictly, it must lose at the transition to the α′ phase. 相似文献
6.
The structure of a crystal was established by X-ray analysis. The solution in the cell of symmetry , with a = 6.6702(5), b = 5.3228(8), c = 8.9091(8) Å, β = 100.546(7)°, Z = 1, has led to R = 0.033 and Rw = 0.036 for 2155 reflections with . This structure can be described as two octahedra-wide ReO3-type slabs connected through “planes” of PO4 tetrahedra. A new structural family KxP2W2nO6n+4 can be foreseen which is closely related to the orthorhombic P4W8O32 and the monoclinic RbxP8W8nO24n+16 series. 相似文献
7.
Paul S. Haradem Bertrand L. Chamberland Lewis Katz Alain Gleizes 《Journal of solid state chemistry》1977,21(3):217-223
A single crystal study of Ba3Pt2O7 shows that the structure tolerates a variable composition which can be written Ba3Pt2+xO7+2x. The crystal studied has a hexagonal cell of dimensions a = 10.108 ± 0.006 Å and c = 8.638 ± 0.009 Å, and a probable space group . The density determined by water displacement is 7.99 g/cm3; the theoretical density for Ba3Pt2O7 is 7.94 g/cm3. The structure was determined from the set of 401 observed independent reflections obtained from 5189 reflections measured by automated counter methods. Refinement on F was carried to a conventional R of 8.0%. The structure has barium-oxygen layers with an essentially four-layer stacking sequence of the double hexagonal (ABAB) type. Platinum is found mainly in face-sharing octahedra, but is also distributed over some sites in which the coordination is nearly square planar and other sites in which the coordination is trigonal prismatic with three PtO bond lengths of 2.00 Å and three long PtO distances of 2.65 Å. The platinum with planar coordination is 0.08 Å from the plane of the four oxygen atoms. 相似文献
8.
The phase diagrams of Ag2SAgI, Ag2SeAgI, Ag2TeAgI, Ag2TeAgBr, and Ag2TeAgCl were investigated. The system Ag2S-AgI shows two broad regions of solid solution which are based on the structure of the high-temperature phases of the constituent compounds. The high-temperature modification of Ag3SI is part of one of these regions. The system Ag2SeAgI resembles the system Ag2TeAgI; both contain limited regions of terminal solid solutions. The AgI-based solid solutions decompose peritectically. In the system Ag2TeAgBr a compound Ag3TeBr was found. Ag3TeBr undergoes a phase transition at 590 ± 20 K. The low-temperature form has hexagonal symmetry with the lattice parameters a = 748.8(1) pm and c = 4357.6(6) pm. The compound Ag5Te2Cl was found in the Ag2TeAgCl system. In both systems a restricted terminal solid solution, based on the high-temperature form of Ag2Te, was observed. Ag5Te2Cl has a reversible phase transformation at 329 ± 3 K with ΔHtr = 9.82 ± 0.4 kJ mole?1. β-Ag5TeCl, the low-temperature form probably has the space group , β = 90.201(1)°, and Z = 4, α-Ag5Te2Cl has the space group with a = 975.5(3), c = 783.0(1) pm, and Z = 4. The anion sublattice is built of octahedra, which share all their vertices with neighboring octahedra. The Ag+ ions are distributed over octahedral holes of this network. The phase is similar in behavior to Ag8GeTe6 and may be a silver-ion conductor. 相似文献
9.
Fe2P2O7 crystallizes in the space group with lattice parameters a = 6.649(2)Å, b = 8.484(2)Å, c = 4.488(1)Å, α = 90.04°, β = 103.89(3)°, γ = 92.82(3)°, and ?cal = 3.86 g/cc. It is essentially isostructural with β-Zn2P2O7. As in the Zn compound, the bridging oxygen atom in the P2O7 group shows a high anisotropic thermal motion. It appears that the P-O-P bond angle is linear as a result of extensive π bonding with the p orbitals on the bridging oxygen atom. The high thermal motion is vibration of the atom into cavities in the structure. 相似文献
10.
The formation of the XeF+ ion by ion-molecule reaction has been observed in an ionized mixture of Xe and NF3 by ion cyclotron resonance mass spectrometry. The excited 2P state of the xenon ion has unambiguously been identified as the major precursor by photoionization mass spectrometry. The NF+3 ion makes an additional minor contribution. Evidence suggests that the excited 2P xenon ion radiatively decays to the 2P ground state on the time scale of the experiment. The transition probability deduced for this dipole forbidden emission, 18 ± 4 s?1, is in good agreement with the theoretical value of 21 s?1 for the sum of the magnetic dipole and electric quadrupole transition rates. 相似文献
11.
Fe2P4O12 has been prepared and identified as an isotype of the other MII2P4O12 tetrametaphosphates (MII = Ni, Mg, Cu, Co, Mn, Cd). Its monoclinic unit cell: contains 4 formula units. The space group is . For tetrametaphosphates with MII = Ni, Mg, Cu, Co, and Mn we found a new denser phase induced at 80 kbar and 1000°C. In the case of Fe2P4O12 the unit cell of this new form is with Z = 2 and two possible space groups Cc or . This dense phase exists at ordinary pressure for the zinc salt. 相似文献
12.
K3Sb3P2O14 crystallizes in the rhombohedral system, space group with a = 7.147(1) Å, c = 30.936(6) Å, Z = 3. The structure was determined from 701 reflections collected on a Nonius CAD4 automatic diffractometer with radiation. The final R index and the weighted Rw index are 0.033 and 0.042, respectively. The structure is built up from layers of SbO6 octahedra and PO4 tetrahedra sharing corners. The potassium ions are situated between the (Sb3P2O14)3? covalent layers. 相似文献
13.
Kjell Waltersson 《Journal of solid state chemistry》1979,28(1):121-131
The crystal structure of has been determined and refined on the basis of three-dimensional X-ray diffractometer data (MoKα radiation). The structure is monoclinic, a = 7.710(2), b = 19.474(7), c = 7.216(2)Å, β = 116.75(1)°, V = 967.5Å3, Z =8, space group Cc (No. 9). The final R and Rw were 0.0295 and 0.0300, respectively, for 1356 independent reflections and 117 variables.The structure contains two crystallographically different VOF5 octahedra linked so as to form complex chains. Two non-equivalent octahedra share one FF edge, forming V2O2F8 doublets. Two F atoms, connected to different V atoms within the doublet, form an edge in the adjacent equivalent V2O2F8 unit thus continuing the chain. The VO distances are 1.583(7) and 1.595(7) Å. The VF distances are in the range 1.881-2.205 Å, mean value: 1.989 Å. The H2O group is a crystal water molecule. 相似文献
14.
Excited iodine atoms I(2P) are formed by laser irradiation of C2F5I at 2950 Å. The mean radiative lifetime τ of these metastable atoms and their bimolecular rate constant k2 for deactivation in collissions with C2F5I were measured to be: τ = 108 ± 10 ms; k2 = (1.8 ± 0.1) × 10?17 cm3/molec s. 相似文献
15.
The details and principles of an apparatus built for measurements of fluorescence quantum yields and cascade-free lifetimes of open-shell cations are reported. These rely on the detection of coincidences between energy selected photoelectrons and undispersed photons. The results of such measurements for CO+2, COS+, CS+2 and N2O+ in selected vibrational levels of their excited states are presented. Non-unity fluorescence quantum yields are found for some vibronic levels of CO+2(), COS+ (), N2OP+() and a non-exponential decay is observed for CS+2(). The data yield the following values for the radiative lifetimes: CO+2() 124 ± 6 ns, CO+2() 140 ± 7 ns, COS+() 550 ± 50 ns and N2O+() 240 ± 12 ns. 相似文献
16.
A new experimental system for atomic resonance spectrometry at λ < 105 nm in a discharge-flow system is described. The spectrum of a fluorine resonance lamp has been studied, and possible precursors for the 2p4 3s excited F atoms formed are suggested. Ground state (2p52P) and J-excited 2P F atoms have been detected for the first time in resonance absorption and fluorescence using the first resonance transitions with wavelengths between 95.2 and 97.8 nm. Preliminary measurements (using both 4P-2P and 2P-2P lines) of the variations with concentration of absorption intensity by ground state F 2P and by J-excited F 2P atoms are reported; F atom concentrations were measured using a titration method based on the rapid reaction, F + Cl2 → FCl + Cl. 相似文献
17.
The crystal structure of SnC2O4 has been determined by X-ray single-crystal techniques and refined to R = 0,018 for 1139 reflections. The cell is monoclinic, space group with Z = 4 formula units, the parameters being a = 10,375(3)Å. b = 5,504(2)Å, c = 8,234(3)Å, β = 125,11(2)°. The oxalato groups, located on symmetry centers, are chelated to two Sn atoms through one oxygen on each carbon atom, giving rise to an infinite string (SnC2O4)n. The Sn(II) atom is one-side bonded to four oxygen atoms with two SnO bonds of 2,232(2) Å and two of 2,393(2) Å. The tin atom is in a distorted trigonal bipyramid SnO4E, the lone pair E occupying one of the apices of the equatorial trigonal base of the polyhedron. Crystal structure comparison with disodium bisoxalatostannate(II), Na2Sn(C2O4)2, permits one to deduce SnC2O4 by crystallographic shear operation of periodicity. Na2Sn(C2O4)2 can be described as an intergrowth of SnC2O4 and Na2C2O4 structures and consldered as the first member of a new series Na2Sn1+n(C2O4)2+n with n integer ? 0. 相似文献
18.
The magnetic interaction in the structural units [Fe2O7]8?, built of two corner-sharing FeO4 tetrahedra, in Na8Fe2O7 () has been studied by magnetic susceptibility measurements (4.2–500 K). An exchange integral of ?37 K is obtained by comparison of the experimental values and the calculated ones using a Heisenberg-Dirac-Van Vleck-type Hamiltonian ? = . The hypothesis of magnetically isolated [Fe2O7]8? groups is corroborated by Mössbauer spectroscopy between 1.5 and 77 K. The susceptibility measurements of the solid solutions Na8Fe2?xMxO7 (M = Al, Ga; 0 ≤ x ≤ 0.2 for Al; 0 ≤ x ≤ 2 for Ga) leads to the same conclusion of the existence of isolated Fe3+Fe3+ pairs in Na8Fe2O7. The type of substitution of Fe by Al or Ga is determined; homonuclear Fe3+Fe3+ and M3+M3+ pairs and heteronuclear Fe3+M3+ pairs are formed. 相似文献
19.
M. Sayer S.L. Segel J. Noad J. Corey T. Boyle R.D. Heyding A. Mansingh 《Journal of solid state chemistry》1982,42(2):191-205
The equilibrium phase diagram for the system of fast-ion electrolyes is established along with the conductivity-composition relationship for polycrystalline samples. The highest conductivity compound (0.07 Ω?1 cm?1 at 300 K) has the composition Ag16I12P2O7. Measurements of relative permittivity and conductivity over a frequency range of 50 Hz to 100 kHz and a temperature range of 77 to 320 K on polycrystalline samples and single crystals of Ag16I12P2O7 show that the conductivity and its temperature dependence is anisotropic, with a higher conductivity along the c axis and a change in the activation energy for conduction from 0.4 eV at low temperatures to 0.14 eV above 300 K. Perpendicular to the c axis the activation energy is constant with temperature (0.28 eV). This anisotropy and a frequency dispersion in the ac conductivity between 110 to 150 K is shown to originate in the crystal structure of the material and in the distribution of Ag+ ions between different sites. 相似文献
20.
Perovskites of the type A2+3B2+M5+2O9, where A2+ = Ba, Sr; B2+ = Mn, Co, Ni, Zn; M5+ = Nb, Ta, show order-disorder phenomena. At lower temperatures a thermodynamically unstable disordered cubic perovskite is formed ( formula unit——in the cell), which transforms irreversibly into a 1: 2 ordered high-temperature form with 3L structure (sequence (c)3). For A2+ = Ba this lattice is hexagonal (space group ; one formula unit in the cell); with A2+ = Sr a triclinic distortion is observed. For Ba3CoNb2O9 a second transformation into a cubic disordered perovskite takes place at 1500°C. This transition is reversible and of the order-disorder type. The vibrational and diffuse reflectance spectra are discussed. 相似文献