共查询到20条相似文献,搜索用时 15 毫秒
1.
The crystal structure of trisodium monophosphate hemihydrate was determined. The space group is and a unit cell contains eight formula units. The unit cell dimensions of are a = 9.631(3), b = 5.416(2), c = 16.938(8) Å, β = 102.60(5)°. The final R value is 0.027 for a set of 1430 independent reflections. This atomic arrangement is mainly a three-dimensional network of distorted NaO6 octahedra. The hydrogen bonding scheme is given. 相似文献
2.
Ninh Nguyen Jacques Choisnet Maryvonne Hervieu Bernard Raveau 《Journal of solid state chemistry》1981,39(1):120-127
Oxygen defect K2NiF4-type oxides have been synthesized for a wide composition range: 0 ≤ x ≤ 1.34. From the X-ray and electron diffraction study three domains have been characterized: orthorhombic compounds with La2CuO4 structure for 0 ≤ x < 0.10, tetragonal oxides similar to LaSrCuO4 for 0.10 ≤ x < 1 and several superstructures derived from the tetragonal cell ( with n = 3, 4, 4.5, 5, 6) for 1 ≤ x ≤ 1.34. The compounds corresponding to 0 < x < 1 differ from the other oxides in that they are characterized by the presence of copper with two oxidation states: + 2 and + 3. A model structure for La0.8Sr1.2CuλO3.4, in which copper has only the + 2 oxidation state, and for which the actual cell is tegragonal—a = 18.804 Å and c = 12.94 Å—has been established. The particular structural evolution of these compounds is discussed in terms of a competition between the capability of Cu(II) to be oxidized to Cu(III) and the ordering of oxygen vacancies. 相似文献
3.
A new hydrate of tungsten trioxide, has been obtained by hydrothermal treatment at 120°C of an aqueous suspension of either tungstic acid gel or crystallized dihydrate. This hydrate has been characterized by different methods. A crystallographic study was carried out from X-ray powder diffraction. The hydrate crystallizes in the orthorhombic system: a = 7.359(3) Å, b = 12.513(6) Å, c = 7.704(5) Å, Z = 12. The existence of structural relationships between the hydrate, , and the product of dehydration, hexagonal WO3, has permitted us to propose a structural model in agreement with the experimental data. must be regarded as an interesting compound because its dehydration leads to a new anhydrous tungsten trioxide, hexagonal WO3. 相似文献
4.
María Vallet-Regí José González-Calbet Miguel A. Alario-Franco Jean-Claude Grenier Paul Hagenmuller 《Journal of solid state chemistry》1984,55(3):251-261
An electron microscopy and diffraction study of several samples of the system shows these solids to be formed by the disordered intergrowth of two out of three of the ordered terms corresponding to , and x = 1 (i.e., LaFeO3, Ca2LaFe3O8, and Ca2Fe2O5). The relative amounts of the intergrowing individuals vary with x and may extend down to unit cell thickness; i.e., to the level of isolated extended defects. 相似文献
5.
Reaction of BaO, Nb2O5, and Nb in mole ratios of 2.4:1.6:1 in an evacuated silica capsule at 1250°C produces a mixture of at least two products, one of which has the probable composition . This compound has an hexagonal unit cell of dimensions a = 9,034 ± 0.004 Å, c = 27.81 ± 0.02 Å, probable space group . Its structure has been determined from 942 independent reflections collected by a counter technique and refined by least squares methods to a conventional R value of 0.062. The basic structure consists of strings of four NbO6 octahedra sharing opposite corners, each string joined to the next by edge sharing of the end octahedra, so that the c axis corresponds to the length of a strand of seven corner-linked octahedra. Chains of three such strands are formed by corner sharing between the strands. The chains in turn are joined by NbO6 octahedra and Si2O7 groups in which the SiOSi linkage is linear. Barium atoms are in sites between the chains coordinated by 13 oxygen atoms. A second site, 15 coordinated, probably has a small amount of barium as well; the fractional occupancy for barium in this site is 0.076. 相似文献
6.
A series of germanate spinels Zn2?x(Ni, Co)xGeO4 has been synthesized and investigated by X-ray diffractometry and infrared spectroscopy. Synthesis at 1200°C leads to cubic phases characterized by an inverse, disordered distribution of Ge and bivalent cations (essentially Ni or Co) over the octahedral sites; however, the presence of some short-range order is suggested by the infrared spectrum. Tempering at an appropriate temperature (between 800 and 900°C, depending on the ratio) leads to tetragonal spinel phases, corresponding to the 1:1 order between Ge and bivalent cation on octahedral sites. The transformation is sluggish and proceeds at a significant rate only in a narrow temperature range, just below the transition temperature. A comparison with the behavior of known inverse, ordered titanate spinels shows that, within the family of inverse II–IV spinels M2IIMIVO4, the ratio of the octahedral cationic radii is one of the factors determining the order-disorder transition temperature, and the importance of the tetragonal distortion. 相似文献
7.
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
8.
Single crystals of a new oxide “FeV3O8” () have been synthesized by slowly cooling a melted mixture with the composition, 8VO2, 3V2O5, Fe2O3. The chemical formula has been determined by electron microprobe analysis. The compound, isostructural with AlNbO4 and VO2(B), has a monoclinic symmetry, space group ; the unit cell dimensions are a = 12.13Å, b = 3.679 Å, c = 6.547 Å, β = 106.85°. A structural refinement based on single crystal data has been carried out. It gave an R-factor of 1.9%. This refinement indicated that the iron and vanadium cations are partially ordered, although the average cation-oxygen distances for the two six-coordinated cations were exactly the same (1.961 Å). This conjecture was supported by the calculation of the cation valences. 相似文献
9.
The proton NMR of a new hydrate as a powder was studied between ?140 and 100°C. The lattice can be considered as “rigid” at temperatures below ?80°C. The structural water corresponding to the above formula is coordinated in the form of water molecules. Above ?80°C it undergoes thermally activated hindered rotation. The compound also retains adsorbed surface “water,” partly in the form of strongly bonded OH groups, partly in the form of water molecules. Degassing at 175°C and 10?4 Torr removes the adsorbed molecular water but leaves OH groups bonded to the surface. 相似文献
10.
The room-temperature diffuse-reflectance spectra of compositions within the Li1+xTi2?xO4 spinel system () show three absorption bands in the range 4000 to 48,000 cm?1. Two high-energy absorption bands correspond to charge-transfer transitions from the oxygen-2p valence band to the titanium t2g and σ1 conduction bands, where the σ1 band of eg character has hybridized titanium-3d and titanium-4s parentage. The absorption band arising from promotion of electrons to the empty σ1 band does not alter with composition whereas the absorption band arising from promotion of electrons to the partially filled t2g band narrows as the concentration of conduction electrons in the t2g band decreases. These two high-energy absorption bands fall entirely within the ultraviolet spectral region, and the absorption edge in occurs at 24,300 cm?1 (3.02 eV). A low-energy absorption band is observed in compositions with and in samples of reduced in hydrogen at elevated temperatures. This band straddles the boundary between the visible and infrared spectral regions and shifts toward lower energy as the concentration of conduction electrons in the t2g band decreases. The possible origins of the band are discussed; the argument is in favor of a d-d interband transition from states in the partially filled t2g band to states in the empty σ1 band. 相似文献
11.
Hans-Peter Abicht Peter Lehniger Kurt Issleib 《Journal of organometallic chemistry》1983,250(1):609-616
The complexes of type R2)2 (M = Pd, Pt) are readily deprotonated by n-Buli under various conditions yielding μ-C-bis-dilithiated species. The resulting carbanions are attacked by the electrophiles Mel, Me3SiCl and Ph2PCl to form the corresponding disubstituted derivatives. The reaction with AuCl . PPh3 yields heterobimetallic complexes with two different MC σ-bonds. The compounds obtained are analytically and spectroscopically characterized. 相似文献
12.
The quasibinary system was investigated in order to derive its thermodynamic and kinetic properties. The phase diagram between 750 and 1000 K was obtained from powder X-ray photographs. The results suggest an order-disorder transition in the phase CdGa2Te4. Reactions were carried out between single crystals of Ga2Te3 and CdTe, between CdTe and CdGa2T4, and between Ga2Te3 and CdGa2Te4. Reaction profiles and growth kinetics were determined by electron microprobe analysis. The morphology of the reaction layer is discussed with respect to the phase diagram and the varying concentration of structural vacancies and their ordering in the product phase CdGa2Te4. 相似文献
13.
The addition of trimethylphosphane to five-membered metallacyclic vinylketone complexes of the type ArR) (I) (Ar = η5-aromatic ring system: C5H5, C5H4Me, C5Me5; R = Me, Et, n-Bu; M = Mo, W) in pentane solution results in the formation of the ylidic metallacyclopropane complexes ArH(COR)] (II). In these 1:1 adducts the three-membered ring is stabilized by an electron-donating phosphonium and an electron-attracting acyl substituent. The negative charge in the ylidic complexes II is localized on the central metal providing it with Lewis base properties. An extraordinary high electron density can be observed on the metal of the derivative C5H5H-(COMe)] (III) which is formed by a 1:2 addition of C5H5W(CO)(C2H2)-(COMe) and PMe3. The metallacyclopropane complexes II and III are characterized by IR, 1H NMR, 13C NMR, 31P NMR and mass spectroscopy. For C5H5H(COMe)], the results of an X-ray structure determination are presented. 相似文献
14.
A time-temperature study has been made of the system: . The isothermal TTT diagram produced demonstrates the course of the transformation sequence, which involves a number of metastable transition alumina intermediate phases. This type of treatment allows calculation of kinetic parameters for the various transformation processes, and these may be correlated with the mechanisms operating. Kinetic aspects of variations in microstructure and crystal structure have also been studied. In particular, the progress of cation migration processes involved in the transformation γ → δ-Al2O3 has been followed in terms of the continuous variation of the spinel subcell parameters. 相似文献
15.
J. Metin D. Chatonier D. Avignant R. Chevalier J.C. Cousseins 《Journal of solid state chemistry》1984,55(3):299-305
A high-temperature phase with the formula has been characterized during the investigation of the CsFLuF3 system. This phase crystallizes in the monoclinic system with unit-cell dimensions a = 13.764(5) Å, b = 7.947(1) Å, c = 4.299(2)Å, β = 90.04(5)° and space group Cm (No. 8), Z = 2. The structure was solved by conventional Patterson and Fourier methods and refined by full-matrix least-squares techniques to a conventional R of 0.053 (Rw = 0.079) for 2038 independent reflections recorded on an automatic four-circle diffractometer. The structure may be regarded as built up of (Lu3F10)? layers that may be described as corner- and edge-shared LuF7 pentagonal bipyramids. These layers run parallel to the (001) plane. The structure extends along the third direction by cornersharing involving axial vertices of the pentagonal bipyramids. This three-dimensional framework delimits tunnels running parallel to the c direction where the Cs+ ions lie. The partial occupancies of both the Cs site and one out of the seven independent fluorine sites results in the nonstoichiometry. 相似文献
16.
The amine substituted phosphines (C6H5)2PN(H)CH2CH3 and (C6H5)2PN(H)CH2C6H5 react with C5H5Fe(CO)2CH(C6H5) (OCH3) photolytically to give moderate yields of the four-membered chelate ring complexes C5H5H (C6H5)] and C5H5H(C6H5)], respectively. Photolysis of C5H5Fe(CO)2CH(C6H5) (OCH3) in the presence of (S)-(?)-diphenyl(1-phenylethylamino)phosphine leads to the isolation of C5H5Fe(CO)[(C6H5)2PNC(CH3) (C6H5)]CH2C6H5 which is proposed to arise from a formally 1,3-hydrogen shift rearrangement of an intermediate four-membered chelate ring complex. 相似文献
17.
It has been observed for several intermetallic compound/H systems that deviations from Sieverts' law of ideal solubility occur which are in the opposite direction from the deviations from ideality which occur in pure metal/H systems. The principal source of nonideality on both types of interstitial solutions arises from the changes of the relative partial molar enthalpy of H2 solution, ΔHH, with H content. The variations of ΔHH with H content are, however, in the opposite directions for intermetallic/H and pure metal/H interstitial solutions. Relative partial molar entropies for solution of H2 in the α-phase of the system are given at 298.2 K. These have been determined from calorimetric determinations of ΔHH and measurements of . The partial entropies show unusual extrema as a function of H content. A model based on trapping of H atoms is proposed which explains the variations of ΔHH and ΔSH. Since the deviations from ideality arising from an increase of ΔHH with H content seem to be limited to solids with at least two different ordered metal components, e.g., intermetallic compounds, it seems reasonable to assign the trapping sites to interstices which result from an interchange of metal atoms. This interchange may create interstices rich in those nearest-neighbor metal atoms which have the greatest affinity for H. 相似文献
18.
19.
G.A. Carriedo J.B.Parra Soto V. Riera X. Solans C. Miravitlles 《Journal of organometallic chemistry》1985,297(2):193-203
The phosphine Ph2PCH2CH2Cl reacts with fac-[XMn(CO)3(dppm)] (X = Cl or Br) in refluxing toluene to give the complexes cis,cis-[XMn(CO)2(dppm)(Ph2PCH2CH2Cl)] (I). Treatment of those species with Na amalgam in THF leads to the alkyl complex [Ph2n(CO)2(dppm)] (II), which does not react with CO under normal conditions but can be converted into cis,cis-[ClMn(CO)2(dppm)(PPh2Et)] by reacting with HCl (g) in ether. If the reduction of I with Na/Hg is carried out in the presence of CO the compound cis-[Ph2n(CO)2(dppm)] (III) is obtained. The latter has also been prepared directly from fac-[BrMn(CO)3(dppm)], Ph2PCH2CH2Cl, and Na/Hg in THF, and characterized by X-ray crystallography. The crystals are monoclinic, space group P21/n; refinement gave R = 0.053 for 2593 reflections with I ? 2.5σ(I). The reaction of the complex fac-[O3ClOMn(CO)3(dppm)] with Ph2PCH2CH2Cl in Cl2CH2 gives the salt fac-[Mn(CO)3(dppm)(Ph2PCH2CH2Cl)]ClO4 which isomerizes to mer-[Mn(CO)3(dppm)(Ph2PCH2CH2Cl)]ClO4 in boiling butanol. Both cationic carbonyl complexes give the acyl species III upon reduction with Na amalgam. 相似文献
20.
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