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1.
A large number of new phases have been prepared and characterized in the MFTlF3 system: Na3TlF6 isostructural with cryolite, Na3Tl2F9, NaxTl1−xF3−2x (0.425 ? x ? 0.565 at 500°C) and Na5Tl9F32 related to the fluorite type, K3TlF6 with a structure similar to that of (NH4)3FeF6, K5Tl3F14 with the chiolite structure, NayTl1−yF3−2y (0.12 ? y ? 0.14 at 500°C) and K2Tl7F23 affiliated to α-UO3, KTlF4, and KTl2F7.  相似文献   

2.
121Sb Mössbauer spectra for M3Sb (M3 = Na3, K3, Na2K, Rb3) were measured at 12 K. The values of isomer shift (d) and quadrupole coupling constant suggest that the valence state of antimony in M3Sb is –3. The d values increase in the order Rb3Sb<K3Sb<Na3Sb<Na2KSb. The differences in d values are discussed by examining M–Sb distances and bond valence for M–Sb interactions. Some covalent interactions between alkali metal atoms and antimony atom are suggested.  相似文献   

3.
The stationary points characterizing the potential energy profiles of the complex processes of the M+(M=H, Li, Na, K) and NF3 were investigated by QCISD and B3LYP in conjunction with the 6-311+G(2d,2p) basis set. The optimized geometries and NBO analysis indicate that the complexes of M+(M=Li, Na, K) and NF3 exist as ion-dipole molecules. But for H+ complexes, there are two stable isomers NF3H+ and NF2+–HF. The interaction distances of isomers follow the sequence H+< Li+< Na+< K+. The calculated affinity energies of the most stable isomers of H+, Li+, Na+, and K+ complexes exceed 20.1 kJ/mol, and these values suggest that the M+–NF3 (M=H, Li, Na, K) complexes could be observed as stable species in gas phase, which supports Fujii's proposal that Li+ ion attachment mass spectrometry can serve as a conceivable technique to quantify the emissions of the NF3.  相似文献   

4.
The Na2O-MgO-B2O3 system (500-550°C) and Rb2O-MgO-B2O3 system (550-700°C) were studied by the methods of powder X-ray diffraction and visual polythermal analysis, and their isothermal sections were constructed at 550 and 650-700°C, respectively. New ternary compounds were found to form: Na24Mg3B10O30, Na4Mg3B2O8, and Rb2Mg3B2O7.  相似文献   

5.
The crystal structures of M+VO3(M+ = K, NH4, and Cs) have been refined using three-dimensional counter-diffractometer X-ray data and full-matrix least-squares methods. The structure of these compounds is characterized by a (V5+O2?3)? chain extending along the c-axis (Pbcm orientation), with adjacent chains linked by the alkali metal cation. The structure may be considered as a variant of the pyroxene structure, and standard atom nomenclature is proposed in order to facilitate comparison with silicate pyroxenes. Structural variation across this series is discussed in detail and is compared with the analogous M+M3+Si2O6 (M+ = Li, Na; M3+ = Al, Cr, Fe, Sc, In) series.  相似文献   

6.
The crystal structure of K2FeO4, which is isomorphous with β-K2SO4, K2MnO4 and K2CrO4, has been determined in detail. In addition, Rb2FeO4 and Cs2FeO4 are shown to be of the same structural type. Crystals of K2FeO4 are orthorhombic, space group Pnma, a = 7.694(5), b = 5.858(7), c = 10.335(7) with Z = 4. The integrated intensities of 1174 independent reflections were measured with an automated diffractometer and refined to a weighted least-squares residue of 0.046. The average tetrahedral [FeO] bond length, corrected for libration effects, is 1.656(6) Å which is equal within experimental error to values observed for [CrO] and [MnO] tetrahedral bonds.  相似文献   

7.
Electron spin resonance spectra of Gd3+ in diluted solid solutions of Gd2O3 in CeO2 have been studied at room temperature for Gd concentrations between 0.01 and 1.00 mol%. While in the case of Mn2+:CeO2 samples, both the linewidth and the line intensity go through a maximum between 0.2 and 0.4% Mn and then start to decrease, in the case of Gd3+:CeO2 samples the linewidth and the line intensity increase monotonically with the dopant concentration. This as taken as evidence that in Gd2O3-CeO2 diluted solid solutions there are no clustering effects similar to the ones observed in Mn:CeO2 solid solutions. It is not clear why clustering effects are present in Mn:CeO2 solid solutions and not in Gd:CeO2 solid solutions; however, it seems reasonable to assume that this is due to the fact that the ionic radius of Mn2+ (81 pm) is about 25% smaller that that of Gd3+ (107.8 pm). In any case, the fact that Gd:CeO2 solid solutions do not exhibit clustering effects means that ESR linewidth data can be used to estimate the concentration of Gd in CeO2 samples, as it is possible to do in several solid solutions of paramagnetic ions in ceramic materials. The results also suggest that the range of the exchange interaction between Gd3+ ions in CeO2 is about 0.89 nm.  相似文献   

8.
Manganites NdM3Sr3Mn4O12 and NdM3Ba3Mn4O12 (M = Li, Na, K) were synthesized by a ceramic method from the corresponding oxides and carbonates. The X-ray diffraction analysis showed that all the compounds crystallized in the tetragonal crystal system with the following lattice parameters: NdLi3Sr3Mn4O12: a = 10.88 ?, c = 9.52 ?, V o = 1126.9 ?3, Z = 4, ρX = 4.95 g/cm3, ρpycn = 4.87 ± 0.05 g/cm3; NdNa3Sr3Mn4O12: a = 10.73 ?, c = 10.66 ?, V o = 1227.3 ?3, Z = 4, ρX = 4.80 g/cm3, ρpycn = 4.73 ± 0.07 g/cm3; NdK3Sr3Mn4O12: a = 10.87 ?, c = 11.71 ?, V o = 1382.6 ?3, Z = 4, ρX = 4.50 g/cm3, ρpycn = 4.43 ± 0.09 g/cm3; NdLi3Ba3Mn4O12: a = 10.97 ?, c = 10.34 ?, V o = 1244.3 ?3, Z = 4, ρX = 5.33 g/cm3, ρpycn = 5.23 ± 0.09 g/cm3; NdNa3Ba3Mn4O12: a = 10.99 ?, c = 11.15 ?, V o = 1346.7 ?3, Z = 4; ρX = 5.11 g/cm3, ρpycn = 5.05 ± 0.06 g/cm3; NdK3Ba3Mn4O12: a = 10.997 ?; c = 13.80 ?, V o = 1668.9 ?3, Z = 4, ρX = 4.32 g/cm3, ρpycn = 4.26 ± 0.07 g/cm3. Original Russian Text ? B.K. Kasenov, E.S. Mustafin, M.A. Akubaeva, S.T. Edil’baeva, Sh.B. Kasenova, Zh.I. Sagintaeva, S.Zh. Davrenbekov, 2009, published in Zhurnal Neorganicheskoi Khimii, 2009, Vol. 54, No. 3, pp. 424–427.  相似文献   

9.
Simultaneous refinements of X-ray and neutron powder diffraction patterns taken on the MUO3 perovskite compounds with M=Na, K and Rb, were performed to reveal anisotropy in the temperature factors, mainly of oxygen. No anisotropic thermal motion was found.The magnetic ordering of the compounds has been investigated with low temperature neutron diffraction. It is found that all these compounds show G-type antiferromagnetic ordering with a similar, orthorhombic magnetic unit cell. The propagation vector could only be determined for the orthorombic NaUO3 compound and was found to point in the z-direction. The refined magnetic moment for U5+ in these structures was found to be around .  相似文献   

10.
Phase formation in the Re-Se-Br-MBr systems (M = K, Rb, Cs) was studied by NMR spectroscopy and powder X-ray diffraction. The reactions taking place in alkali metal halide melts were found to give, among the series of cluster anions [{Re6Se8 − n Br n }Br6](4 − n)− (0 ≤ n≤ 4), polymeric complexes Re6Se8Br 2 and M2Re6Se8Br4 (M = Cs, Rb) and salts containing cluster anions [Re6Se6Br8]2− and [Re6Se7Br7]3− as the major products. The effect of the alkali metal cation on the product composition and ratio was established. Original Russian Text ? S.S. Yarovoi, Yu.V. Mironov, S.V. Tkachev, V.E. Fyodorov, 2009, published in Zhurnal Neorganicheskoi Khimii, 2009, Vol. 54, No. 2, pp. 344–349.  相似文献   

11.
The 19F NMR spectra of π-allyl-tris(trifluorophosphine)rhodium(I), [A], benzene-tris(trifluorophosphine)chromium(0), [B], and nitrosyl-tris(trifluorophosphine) rhodium(-I), [C], are presented. These are examples of [AX3]3 nuclear spin systems (A = phosphorus, X = fluorine). The spectra of [A] and [B] have been completely analysed to afford values of 1J(PF), 2J(PP′), 3J(PF′) and 4J(FF′).  相似文献   

12.
ESR experiments on the luminescent triplet state of triclinic K2Cr2O7 are reported. For the A site D = 24.300, E = 2.324 GHz, for t  相似文献   

13.
研究了LiZr2(PO4)3在水溶液中的Na/Li和Ag/Li离子交换行为.结果表明,LiZr2(PO4)3对Na+和Ag+离子均具有很高的选择性,且对Ag+的选择性高于Na+.LiZr2(PO4)3与Ag+的离子交换反应是通过形成固溶体的形式进行的,而与Na+的离子交换反应则是通过置换进行的.温度升高有利于提高LiZr2(PO4)3上Na/Li和Ag/Li的离子交换反应速度.  相似文献   

14.
J.J. Zeilstra  J.B.F.N. Engberts   《Tetrahedron》1973,29(24):4299-4302
Syn- andanti-α-sulfonyl iminoxy radicals have been generatedin situ by lead tetra-acetate oxidation of α-oximino sulfones. The ESR spectra of the geometrical isomers have been assigned and the14N and1H hyperfine splitting constants are discussed in terms of the proposed structures.  相似文献   

15.
ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.  相似文献   

16.
Three new quaternary selenites, A2SeMoO6 (A=Na+, K+, or Rb+), were synthesized through the solid-state reaction of A2MoO4 with SeO2 at 400°C. Although the reported materials are ‘stoichiometrically equivalent’, the compounds exhibit strikingly different crystal structures. Whereas Na2SeMoO6 has a three-dimensional crystal structure, K2SeMoO6 and Rb2SeMoO6 are molecular and uni-dimensional, respectively. However, all of the new materials have structures containing Mo6+ octahedra linked to Se4+ trigonal pyramids. Although the Mo6+ and Se4+ cations are in local asymmetric environments in all three materials, only Na2SeMoO6 is non-centrosymmetric. Single crystal X-ray data: Na2SeMoO6, cubic, space group, P213 (no. 198), a=8.375(5) Å, Z=4, R(F)=0.0143; K2SeMoO6, monoclinic, space group, P21/c (no. 14), a=6.118(8) Å, b=15.395(2) Å, c=7.580(9) Å, β=112.39(4)°, Z=4, R(F)=0.0281; Rb2SeMoO6, orthorhombic, space group, Pnma (no. 62), a=7.805(9) Å, b=6.188(7) Å, c=14.405(4) Å, Z=4, R(F)=0.0443.  相似文献   

17.
Density functional theory calculations within the generalized-gradient approximation are used to establish the ground-state structure, equilibrium structural parameters, and electronic structure for MBeH(3) phases. From the 24 structural arrangements used as inputs for structural optimization calculations, the ground-state crystal structures of MBeH(3) phases have been predicted. At ambient conditions, LiBeH(3) and NaBeH(3) crystallize with perovskite-related orthorhombic and cubic structures, respectively. The remaining phases KBeH(3), RbBeH(3), and CsBeH(3) crystalize in a monoclinic structure. In the predicted phases one can store up to 15.93 wt % of hydrogen. The formation energy for the MBeH(3) phases have been investigated along different reaction pathways. The electronic structures reveal that all these phases are insulators with estimated band gaps varying between 1.79 and 3.44 eV.  相似文献   

18.
An improved method of synthesis of hexakis(trifluorophosphine)chromium(0), -molybdenum(0)and -tungsten(0) is described, involving photochemically induced substituion of carbonyl groups from the (trifluorophosphine)tricarbonylmetallates by PF3 under moderate pressure. A full analysis of the fragmentation patterns in a mass spectrometer is given, and both Raman and infrared data obtained throughoutthe range 4000–50 cm?1 are discussed. Complete vibrational mode assignments are made, and a normal coordinate analysis leading to the determination of force constants and potential energy distributions is presented. The normal mode in which M-P bond stretching is predominant in all cases involves a significant contribution from PF bond stretching in these molecules.  相似文献   

19.
The solid-state reactions of UO3 and WO3 with M2CO3 (M=Na, K, Rb) at 650°C for 5 days result, accordingly the starting stoichiometry, in the formation of M2(UO2)(W2O8) (M=Na (1), K (2)), M2(UO2)2(WO5)O (M=K (3), Rb (4)), and Na10(UO2)8(W5O20)O8 (5). The crystal structures of compounds 2, 3, 4, and 5 have been determined by single-crystal X-ray diffraction using Mo(Kα) radiation and a charge-coupled device detector. The crystal structures were solved by direct methods and Fourier difference techniques, and refined by a least-squares method on the basis of F2 for all unique reflections. For (1), unit-cell parameters were determined from powder X-ray diffraction data. Crystallographic data: 1, monoclinic, a=12.736(4) Å, b=7.531(3) Å, c=8.493(3) Å, β=93.96(2)°, ρcal=6.62(2) g/cm3, ρmes=6.64(1) g/cm3, Z=4; 2, orthorhombic, space group Pmcn, a=7.5884(16) Å, b=8.6157(18) Å, c=13.946(3) Å, ρcal=6.15(2) g/cm3, ρmes=6.22(1) g/cm3, Z=8, R1=0.029 for 80 parameters with 1069 independent reflections; 3, monoclinic, space group P21/n, a=8.083(4) Å, b=28.724(5) Å, c=9.012(4) Å, β=102.14(1)°, ρcal=5.83(2) g/cm3, ρmes=5.90(2) g/cm3, Z=8, R1=0.037 for 171 parameters with 1471 reflections; 4, monoclinic, space group P21/n, a=8.234(1) Å, b=28.740(3) Å, c=9.378(1) Å, β=104.59(1)°, ρcal=6.13(2) g/cm3,  g/cm3, Z=8, R1=0.037 for 171 parameters with 1452 reflections; 5, monoclinic, space group C2/c, a=24.359(5) Å, b=23.506(5) Å, c=6.8068(14) Å, β=94.85(3)°, ρcal=6.42(2) g/cm3,  g/cm3, Z=8, R1=0.036 for 306 parameters with 5190 independent reflections. The crystal structure of 2 contains linear one-dimensional chains formed from edge-sharing UO7 pentagonal bipyramids connected by two octahedra wide (W2O8) ribbons formed from two edge-sharing WO6 octahedra connected together by corners. This arrangement leads to [UW2O10]2− corrugated layers parallel to (001). Owing to the unit-cell parameters, compound 1 probably contains similar sheets parallel to (100). Compounds 3 and 4 are isostructural and the structure consists of bi-dimensional networks built from the edge- and corner-sharing UO7 pentagonal bipyramids. This arrangement creates square sites occupied by W atoms, a fifth oxygen atom completes the coordination of W atoms to form WO5 distorted square pyramids. The interspaces between the resulting [U2WO10]2− layers parallel to plane are occupied by K or Rb atoms. The crystal structure of compound 5 is particularly original. It is based upon layers formed from UO7 pentagonal bipyramids and two edge-shared octahedra units, W2O10, by the sharing of edges and corners. Two successive layers stacked along the [100] direction are pillared by WO4 tetrahedra resulting in sheets of double layers. The sheets are separated by Na+ ions. The other Na+ ions occupy the rectangular tunnels created within the sheets. In fact complex anions W5O2010− are built by the sharing of the four corners of a WO4 tetrahedron with two W2O10 dimmers, so, the formula of compound 5 can be written Na10(UO2)8(W5O20)O8.  相似文献   

20.
《Polyhedron》1986,5(3):821-832
Raman and IR spectra were obtained of molten AlCl3NH3, AlCl3ND3 and AlBr3NH3 in addition to chloroaluminate mixtures of the AlCl3NH3. The main spectral features of the gaseous AlCl3NH3 molecules having a C3v-symmetry are retained in the molten and glassy states. Some additional bands were observed both in the pure liquid and in mixtures with chloroaluminate melts. The spectra indicated that the discussion reaction 2AlCl3NH3 = AlCl4 + [AlCl2(NH3)2]+ occurs with K ⋍ 3 × 10−3 (mole fraction basis). Frequency shifts found on liquefaction demonstrate that extensive hydrogen bonding takes place between AlCl3NH3 molecules. This observation is supported by the glass-forming nature of AlCl3NH3. The molecule Al2Cl6NH3 seems to exist in binary AlCl3-AlCl3NH3 melts.  相似文献   

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