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1.
The crystal structures of hydrothermally synthesized (T = 493 K, 7–9 d) rubidium aluminium bis[hydrogen arsenate(V)], RbAl(HAsO4)2, caesium iron bis[hydrogen arsenate(V)], CsFe(HAsO4)2, rubidium dialuminium arsenic(V) hexakis[hydrogen arsenate(V)], RbAl2As(HAsO4)6, and caesium diiron arsenic(V) hexakis[hydrogen arsenate(V)], CsFe2As(HAsO4)6, were solved by single‐crystal X‐ray diffraction. The four compounds with the general formula M+M3+(HAsO4)2 adopt the RbFe(HPO4)2 structure type (Rc) and a closely related new structure type, which is characterized by a different stacking order of the building units, leading to noncentrosymmetric space‐group symmetry R32. The second new structure type, with the general formula M+M3+2As(HAsO4)6 (Rc), is also a modification of the RbFe(HPO4)2 structure type, in which one third of the M3+O6 octahedra are replaced by AsO6 octahedra, and two thirds of the voids in the structure, which are usually filled by M+ cations, remain empty to achieve charge balance.  相似文献   

2.
The crystal structures among M1–M2–(H)‐arsenites (M1 = Li+, Na+, K+, Rb+, Cs+, Ca2+, Sr2+, Ba2+, Cd2+, Pb2+; M2 = Mg2+, Mn2+,3+, Fe2+,3+, Co2+, Ni2+, Cu2+, Zn2+) are less investigated. Up to now, only the structure of Pb3Mn(AsO3)2(AsO2OH) was described. The crystal structure of hydrothermally synthesized Na4Cd7(AsO3)6 was solved from the single‐crystal X‐ray diffraction data. Its trigonal crystal structure [space group R$\bar{3}$ , a = 9.5229(13), c = 19.258(4) Å, γ = 120°, V = 1512.5(5) Å3, Z = 3] represents a new structure type. The As atoms are arranged in monomeric (AsO3)3– units. The surroundings of the two crystallographically unique sodium atoms show trigonal antiprismatic coordination, and two mixed Cd/Na sites are remarkably unequal showing tetrahedral and octahedral coordinations. Despite the 3D connection of the AsO3 pyramids, (Cd,Na)Ox polyhedra and NaO6 antiprisms, a layer‐like arrangement of the Na atoms positioned in the hexagonal channels formed by CdO4 deformed tetrahedra and AsO3 pyramids in z = 0, 1/3, 2/3 is to be mentioned. These pseudo layers are interconnected to the 3D network by (Cd,Na)O6 octahedra. Raman spectra confirmed the presence of isolated AsO3 pyramids.  相似文献   

3.
Ba10−x Cs x (PO4)6Cl2, (x = 0, 0.5) chloroapatite ceramics were prepared by sonochemical method of synthesis. The measured room temperature lattice parameters of Ba10 (PO4)6Cl2 and Ba9.5Cs0.5 (PO4)6Cl2−δ are practically the same; that is, a = 10.26 (8), c = 7.65 (7) and a = 10.27 (7), c = 7.65 (5), respectively. Heat capacity measurements were carried out on these materials by differential scanning calorimetry (DSC) in the temperature range 298–800 K. The heat capacity values of Ba9.5Cs0.5(PO4)6Cl2−δ are found to be slightly higher at all temperatures than those of Ba10(PO4)6Cl2. From the heat capacity data, other thermodynamic functions such as enthalpy and entropy increments were computed. The heat capacity values of Ba10(PO4)6Cl2 and Ba9.5Cs0.5(PO4)6Cl2−δ at 298 K are 0.3912 and 0.4310 J K−1 g−1, respectively. Thermal expansion property of the doped and undoped barium chloroapatites was measured by using a home built dilatometer which uses LVDT as displacement sensor. The bulk thermal expansion of Ba10(PO4)Cl2 and Ba9.5Cs0.5(PO4)Cl2−δ is observed to be about 0.9% in the temperature range of 298–973 K.  相似文献   

4.
A new compound, heptamagnesium bis­(arsenate) tetrakis(hydrogenarsenate), Mg7(AsO4)2(HAsO4)4, was synthesized by a hydro­thermal method. The structure is based on a three‐dimensional framework of edge‐ and corner‐sharing MgO6, MgO4(OH)2, MgO5, AsO3(OH) and AsO4 polyhedra. Average Mg—O and As—O bond lengths are in the ranges 2.056–2.154 and 1.680–1.688 Å, respectively. Each of the two non‐equivalent OH groups is bonded to both an Mg and an As atom. One OH group is involved in a very short hydrogen bond [O⋯O = 2.468 (3) Å]. The formula unit is centrosymmetric, with all atoms in general positions except for one Mg atom, which has site symmetry . The compound is isotypic with Mn7(AsO4)2(HAsO4)4 and M7(PO4)2(HPO4)4, where M is Fe, Co or Mn.  相似文献   

5.
The crystal structure of hydro­thermally synthesized caesium aluminium bis­[dihydrogen arsenate(V)] hydrogen arsen­ate(V), CsAl(H2AsO4)2(HAsO4), was determined from single‐crystal X‐ray diffraction data collected at room temperature. The compound represents a new structure type that is characterized by decorated kröhnkite‐like [100] chains of corner‐sharing AlO6 octa­hedra and AsO4 tetra­hedra. Ten‐coordinated Cs atoms are situated between the chains, which are inter­connected by five different hydrogen bonds [O⋯O = 2.569 (4)–2.978 (4) Å]. All atoms are in general positions. CsAl(H2AsO4)2(HAsO4) is very closely related to CsGa(H1.5AsO4)2(H2AsO4) and isotypic CsCr(H1.5AsO4)2(H2AsO4).  相似文献   

6.
The crystal structures of caesium dihydrogen arsenate(V) bis[trihydrogen arsenate(V)], Cs(H2AsO4)(H3AsO4)2, ammonium dihydrogen arsenate(V) trihydrogen arsenate(V), NH4(H2AsO4)(H3AsO4), and dilithium bis(dihydrogen phosphate), Li2(H2PO4)2, were solved from single‐crystal X‐ray diffraction data. NH4(H2AsO4)(H3AsO4), which was hydrothermally synthesized (T = 493 K), is homeotypic with Rb(H2AsO4)(H3AsO4), while Cs(H2AsO4)(H3AsO4)2 crystallizes in a novel structure type and Li2(H2PO4)2 represents a new polymorph of this composition. The Cs and Li compounds grew at room temperature from highly acidic aqueous solutions. Li2(H2PO4)2 forms a three‐dimensional (3D) framework of PO4 tetrahedra sharing corners with Li2O6 dimers built of edge‐sharing LiO4 groups, which is reinforced by hydrogen bonds. The two arsenate compounds are characterized by a 3D network of AsO4 groups that are connected solely via multiple strong hydrogen bonds. A statistical evaluation of the As—O bond lengths in singly, doubly and triply protonated AsO4 groups gave average values of 1.70 (2) Å for 199 As—OH bonds, 1.728 (19) Å for As—OH bonds in HAsO4 groups, 1.714 (12) Å for As—OH bonds in H2AsO4 groups and 1.694 (16) Å for As—OH bonds in H3AsO4 groups, and a grand mean value of 1.667 (18) Å for As—O bonds to nonprotonated O atoms.  相似文献   

7.
The crystal structures of hydrothermally synthesized aluminium dihydrogen arsenate(V) dihydrogen diarsenate(V), Al(H2AsO4)(H2As2O7), gallium dihydrogen arsenate(V) dihydrogen diarsenate(V), Ga(H2AsO4)(H2As2O7), and diindium bis[dihydrogen arsenate(V)] bis[dihydrogen diarsenate(V)], In2(H2AsO4)2(H2As2O7)2, were determined from single‐crystal X‐ray diffraction data collected at room temperature. The first two compounds are representatives of a novel sheet structure type, whereas the third compound crystallizes in a novel framework structure. In all three structures, the basic building units are M 3+O6 octahedra (M = Al, Ga, In) that are connected via one H2AsO4 and two H2As2O72− groups into chains, and further via H2As2O72− groups into layers. In Al/Ga(H2AsO4)(H2As2O7), these layers are interconnected by weak‐to‐medium–strong hydrogen bonds. In In2(H2AsO4)2(H2As2O7)2, the H2As2O72− groups link the chains in three dimensions, thus creating a framework topology, which is reinforced by weak‐to‐medium–strong hydrogen bonds. The three title arsenates represent the first compounds containing both H2AsO4 and H2As2O72− groups.  相似文献   

8.
Sodium zirconium arsenate phosphates NaZr2(AsO4) x (PO4)3?x were synthesized by precipitation technique and studied by X-ray diffraction and IR spectroscopy. In the series of NaZr2(AsO4) x (PO4)3?x , continuous substitution solid solutions are formed (0 ≤ x ≤ 3) with the mineral kosnarite structure. The crystal structure of NaZr2(AsO4)1.5(PO4)1.5 was refined by full-profile analysis: space group R \(\bar 3\) c, a = 8.9600(4)Å, c = 22.9770(9) Å, V = 1597.5(1) Å3, R wp = 4.55. The thermal expansion of the arsenate-phosphate NaZr2(AsO4)1.5(PO4)1.5 and the arsenate NaZr2(AsO4)3 was studied by thermal X-ray diffraction in the temperature range of 20–800°C. The average linear thermal expansion coefficients (αav = 2.45 × 10?6 and 3.91 × 10?6 K?1, respectively) indicate that these salts are medium expansion compounds.  相似文献   

9.
The title compound, N,N,N′,N′‐tetra­methyl­ethyl­enedi­ammon­ium di­aqua­(arsenate)­(hydrogen arsenate)­dizinc(II), (C6H18N2)0.5[Zn2(AsO4)(HAsO4)(H2O)2], is a new zincoarsenate obtained by hydro­thermal synthesis. The structure consists of infinite two‐dimensional anionic layers alternating with planes containing centrosymmetric organic diprotonated template N,N,N′,N′‐tetra­methyl­ethyl­enedi­ammonium cations, [H3N­C6H12NH3]2+. The latter are interconnected to the framework through hydrogen bonds.  相似文献   

10.
Mixed amorphous, glassy type, zirconium-titanium arsenate (ZrTiAs) and hafniumtitanium arsenate (HfTiAs) have been prepared. The composition and exchange capacity of the prepared samples were investigated in comparison with pure zirconium, titanium and hafnium arsenates, respectively. For the samples the ZrxTi(1-x)(HAsO4)2·2H2O and the HfxTi(1-x)(HAsO4)2·2H2O compositions (where 0<x<1) were found. The exchange capacity values were found less than those for pure arsenates, but they do not change their values under the effect of high dose of gamma-radiation.  相似文献   

11.
The novel hydrothermally synthesized title compound, pentabarium tetrachloride octahydrate octakis(oxovanadium phosphate), Ba5Cl4(H2O)8(VPO5)8, crystallizes in the orthorhombic space group Cmca with a unit cell containing four formula units. Two Ba2+ cations, two Cl anions and the O atoms of four water molecules are situated on the (100) mirror plane, while the third independent Ba2+ cation is on the intersection of the (100) plane and the twofold axis parallel to a. Two phosphate P atoms are on twofold axes, while the remaining independent P atom and both V atoms are in general positions. The structure is characterized by two kinds of layers, namely anionic oxovanadium phosphate (VPO5), composed of corner‐sharing VO5 square pyramids and PO4 tetrahedra, and cationic barium chloride hydrate clusters, Ba5Cl4(H2O)8, composed of three Ba2+ cations linked by bridging chloride anions. The layers are connected by Ba—O bonds to generate a three‐dimensional structure.  相似文献   

12.
Calcium–cadmium chlorapatites solid solutions with the general formula Ca10–xCdx(PO4)6Cl2,1≤x≤10, were prepared by solid state reaction and characterized by X-ray diffraction, infrared spectroscopy and chemical analysis. Using an isoperibol calorimeter, their enthalpies of solution in 9 mass% nitric acid were measured. In order to determine the enthalpies of formation and enthalpies of mixing, thermochemical cycles were proposed and complementary experiences were performed. The results obtained show a decrease of the enthalpy of formation with the amount of cadmium introduced in the lattice. The variation of mixing enthalpy vs. x=Cd/(Cd+Ca) shows a maximum at about x=0,4. This could be explained by the existence of two cationic sites in the phosphoapatite structure. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

13.
Smog chamber/Fourier transform infrared (FTIR) techniques were used to measure the kinetics of the reaction of n‐CH3(CH2)xCN (x = 0–3) with Cl atoms and OH radicals: k(CH3CN + Cl) = (1.04 ± 0.25) × 10−14, k(CH3CH2CN + Cl) = (9.20 ± 3.95) × 10−13, k(CH3(CH2)2CN + Cl) = (2.03 ± 0.23) × 10−11, k(CH3(CH2)3CN + Cl) = (6.70 ± 0.67) × 10−11, k(CH3CN + OH) = (4.07 ± 1.21) × 10−14, k(CH3CH2CN + OH) = (1.24 ± 0.27) × 10−13, k(CH3(CH2)2CN + OH) = (4.63 ± 0.99) × 10−13, and k(CH3(CH2)3CN + OH) = (1.58 ± 0.38) × 10−12 cm3 molecule−1 s−1 at a total pressure of 700 Torr of air or N2 diluents at 296 ± 2 K. The atmospheric oxidation of alkyl nitriles proceeds through hydrogen abstraction leading to several carbonyl containing primary oxidation products. HC(O)CN, NCC(O)OONO2, ClC(O)OONO2, and HCN were identified as the main oxidation products from CH3CN, whereas CH3CH2CN gives the products HC(O)CN, CH3C(O)CN, NCC(O)OONO2, and HCN. The oxidation of n‐CH3(CH2)xCN (x = 2–3) leads to a range of oxygenated primary products. Based on the measured OH radical rate constants, the atmospheric lifetimes of n‐CH3(CH2)xCN (x = 0–3) were estimated to be 284, 93, 25, and 7 days for x = 0,1, 2, and 3, respectively.  相似文献   

14.
Nasicon-type trisodium discandium tris­(arsenate), Na3Sc2(AsO4)3, contains a polyhedral network of vertex-sharing octahedral ScO6 and tetrahedral AsO4 units [dav(Sc—O) = 2.089 (2) Å and dav(As—O) = 1.672 (2) Å] encapsulating two types of Na+ species. The sodium site occupancies are similar to those of the equivalent species in β-Na3Sc2(PO4)3.  相似文献   

15.
Two new barium borate bromide crystals, Ba2BO3Br and Ba3BO3Br3, have been obtained by spontaneous crystallization. Ba2BO3Br crystallizes in P−3m1 space group, with cell parameters of a = 5.5157(10) Å, c = 11.019(4) Å, and Z = 2, its structure is build up by alternately stacking along c-axis of [Ba2(BO3)2]2− layers and bromide [Ba2Br2]2+ layers. The solved structure is analog to Ba2(BO3)1−x(CO3)xCl1+x except the interstitial halogen atoms at (0, 0, 1/2) is missing and accordingly the partly CO3 substitution for BO3 has not been observed. Ba3BO3Br3 crystallizes in a new structure type with P−1 space group and cell parameters of a = 9.280(4) Å, b = 9.349(7) Å, c = 13.025(9) Å, α = 92.71(3)°, β = 98.29(3)°, γ = 116.200(18)° and Z = 4. The basic structural unit in Ba3BO3Br3 is the clusters composed of 4 BO3 groups and 12 Ba atoms, which in turn are linked by eight Ba–O bonds with other four clusters to form sheets extend in the (001) plane.  相似文献   

16.
IR and Raman spectra of Te(OH)6.2NH4H2AsO4.(NH4)2HAsO4 (compound I) and Te(OH)6.2(NH4)2HAsO4 (compound II) are recorded and analysed. The symmetry of different groups and the vibrational interaction between them are discussed. The observed spectra suggest the existence of HAsO2−4 in II and coexistence of HAsO2−4 and H2AsO4 in I. The ammonium ion is found to execute hindered rotation in the lattice in both the compounds.  相似文献   

17.
The previously uninvestigated atomic arrangements of six strontium arsenate(V) phases in the systems Sr-As-O-X (X = H, Cl) have been determined. Single crystals of Sr3(AsO4)2 and Sr5(AsO4)3Cl were grown from a borate and NaCl melt, respectively, whereas single crystals of α- and β-SrAs2O6 and of Sr5-(AsO4)3OH were obtained under hydrothermal conditions. Microcrystalline samples of Sr2As2O7 were prepared by solid-state reaction of As2O5 with SrCO3 and, alternatively, by thermolysis of SrHAsO4. Crystal structure determinations based on powder X-ray diffraction data using the Rietveld method (Sr2As2O7), and from single-crystal X-ray diffraction data (all other phases) revealed isotypism with known structure types (except β-SrAs2O6 which represents a new structure type). Sr3(AsO4)2 crystallizes in the K2Pb(SO4)2 structure type; Sr2As2O7 is isotypic with the high-temperature polymorphs of Ca2P2O7 and Sr2V2O7, but itself shows no polymorphism; Sr5(AsO4)3OH and Sr5(AsO4)3Cl crystallize with the hydroxylapatite and chloroapatite structure, respectively; SrAs2O6 is dimorphic. Like all other known MIIAs2O6 metaarsenates (M = Mn, Co, Ni, Sr, Pd, Cd, Hg, Pb), the α-polymorph crystallizes in the PbSb2O6 structure type, whereas the novel β-polymorph is the first example of a MIIAs2O6 superstructure with a doubled c-axis. Additional analytical methods using Raman spectroscopy and thermal analyses support the results of the X-ray structure work.  相似文献   

18.
MZr2(AsO4)3 arsenates and MZr2(AsO4) x (PO4)3 ? x arsenate phosphates (M = K, Rb, Cs) have been obtained by sol-gel synthesis followed by heat treatment and have been characterized by X-ray diffraction, electron probe microanalysis, and IR spectroscopy. Continuous series of substitutional solid solutions form in the MZr2(AsO4) x (PO4)3 ? x systems (0 ≤ x ≤ 3). The solid solutions have a kosnarite structure (KZr2(PO4)3, space group \(R\bar 3c\) ). The crystal structures of MZr2(AsO4)3 and MZr2(AsO4)1.5(PO4)1.5 have been refined by full-profile analysis. The structural frameworks of these phases are built from ZrO6 octahedra and AsO4 tetrahedra or (As,P)O4 tetrahedra statistically populated by arsenic and phosphorus atoms. The alkali metal atoms occupy extraframework sites. The effect of the crystal chemical properties of alkali metals on the formation of the structures of MZr2(AsO4)3 arsenates (M = Li-Cs) and MZr2(AsO4) x (PO4)3 ? x solid solutions is discussed.  相似文献   

19.
The title compound, tetrasodium cobalt aluminium hexaarsenate, Na4Co7−xAl2/3x(AsO4)6 (x = 1.37), is isostructural with K4Ni7(AsO4)6; however, in its crystal structure, some of the Co2+ ions are substituted by Al3+ in a fully occupied octahedral site (site symmetry 2/m) and a partially occupied tetrahedral site (site symmetry 2). A third octahedral site is fully occupied by Co2+ ions only. One of the two independent tetrahedral As atoms and two of its attached O atoms reside on a mirror plane, as do two of the three independent Na+ cations, all of which are present at half‐occupancy. The proposed structural model based on a careful investigation of the crystal data is supported by charge‐distribution (CHARDI) analysis and bond‐valence‐sum (BVS) calculations. The correlation between the X‐ray refinement and the validation results is discussed.  相似文献   

20.
Two modifications of (TeO)(HAsO4) were obtained by reacting tellurium dioxide with arsenic acid under boiling conditions (modification I, acid concentration 80 wt‐%) or under hydrothermal conditions (modification II, acid concentration 50 wt‐%). The crystal structures of the two modifications were determined from single‐crystal X‐ray data [modification I: P21/c, Z = 4, a = 7.4076(10), b = 5.9596(7), c = 9.5523(11) Å, β = 102.589(8)°, 2893 structure factors, 68 parameters, R[F2 > 2σ(F2)] = 0.0247, wR2(F2 all) = 0.0530; modification II: P21/c, Z = 4, a = 6.2962(4), b = 4.7041(3), c = 13.9446(8) Å, β = 94.528(3)°, 2549 structure factors, 69 parameters, R[F2 > 2σ(F2)] = 0.0207, wR2(F2 all) = 0.0462)]. Dehydration of (TeO)(HAsO4)‐II at temperatures above 260 °C results in the formation of polycrystalline (Te3O3)(AsO4)2. Single crystals of the anhydrous product were grown either by heating stoichiometric amounts of the binary oxides TeO2 and As2O5 in closed silica glass ampoules or with higher concentrated arsenic acid (80 wt‐%) under hydrothermal conditions at 220 °C. The common features in the crystal structures of (Te3O3)(AsO4)2 [P$\bar{1}$ , Z = 4, a = 6.5548(4), b = 7.6281(6), c = 15.0464(15) Å, α = 140.212(6), β = 102.418(9)°, γ = 77.346(5)°, 5718 structure factors, 146 parameters, R[F2 > 2σ(F2)] = 0.0351, wR2(F2 all) = 0. 1093] and in that of the two modifications of acidic (TeO)(HAsO4) are [TeO5] square‐pyramids and [AsO4] tetrahedra. In anhydrous (Te3O3)(AsO4)2 and in (TeO)(HAsO4)‐II, a layered arrangement of the building units is found, whereas in the (TeO)(HAsO4)‐I structure strands are formed. Different hydrogen bonding interactions are present in the two modifications of (TeO)(HAsO4).  相似文献   

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