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1.
《Journal of solid state chemistry》1986,61(2):263-268
The heat capacities of MnCl2·2H2O and MnCl2·2D2O have been experimentally determined from 1.4 to 300 K. The smooth heat capacity and the thermodynamic functions (H°T − H°0) and S°T are reported for the two compounds over the 10 and 300 K temperature range. The error in the thermodynamic functions at 10 K is estimated at 3%. Additional error in the tabulated values arising from the heat capacity data above 10 K is thought to be less than 1%. Lambda-shaped heat capacity features associated with antiferromagnetic ordering were observed at 6.67 ± 0.08 and 6.61 ± 0.08 K for the dihydrate and dideuterate, respectively. In addition, compound heat capacity anomalies consisting of a small lambda-shaped feature at 57.7 ± 0.5 K with a comparably large high-temperature shoulder extending to approximately 70 K were observed in both the dihydrate and dideuterate. The entropies associated with these anomalies are 0.42 ± 0.04 and 1.04 ± 0.04 J/mole-K, respectively. 相似文献
2.
R. O. Grishchenko A. L. Emelina 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2013,87(1):1-5
A pure phase of monosodium aluminate hydrate Na2O · Al2O3 · 2.5H2O (MAH) is synthesized and characterized by means of XRD, IR, SEM, TGA, and DSC. The heat capacity of the compound is measured in the temperature range of ?100 to 100°C, and the thermal contributions to enthalpy and entropy are calculated. The standard entropy, enthalpy, and Gibbs energy of formation of MAH at 298 K are estimated. 相似文献
3.
《Solid State Sciences》2000,2(2):205-214
The synthesis and crystal structure of a novel hydrated magnesium diphosphate and its high temperature variant are described. Both structures were solved from powder X-ray diffraction data. The room temperature variant with composition Mg2P2O7·3.5H2O crystallises in the monoclinic space group P21/c (No. 14) with a=10.9317(1), b=8.05578(9), c=9.2774(1) Å, β=90.201(1)°, V=816.99(2) Å3 and Z=4. The structure consists of sheets stacked along [100] which are linked through MgO2(H2O)4 pillars into a three-dimensional framework with cavities containing water molecules. Within the sheets there are infinite edge-sharing chains of Mg octahedra along [010] which are cross linked by P2O74− groups. A high temperature variant exists around 200°C. The crystal structure of this compound with composition Mg2P2O7·H2O was solved and refined in the monoclinic space group C2/c (No. 15) with a=18.6596(4), b=7.9769(1), c=8.9757(2) Å, β=107.378(1)°, V=1275.01(4) Å3, Z=8. The transformation to Mg2P2O7·H2O involves removal of the water molecules in the cavities and the water molecules of the Mg octahedral pillars in Mg2P2O7·3.5H2O. The sheets in Mg2P2O7·3.5H2O however remain unchanged during the transformation as the water molecule coordinating Mg here is retained. These sheets are linked through tetrahedral MgO4 pillars into a three-dimensional structure containing infinite 10-membered ring channels along [001]. Both compounds have been further characterised by 31P MAS NMR spectroscopy, thermogravimetric analysis and high temperature powder X-ray diffraction. 相似文献
4.
《Chemical physics letters》1986,124(3):274-278
We have recorded the photoelectron spectra of the gas phase negative ions N2O− and (N2O)2− both of which were prepared in a nozzle ion source. The shift between the maxima of the two spectra is interpreted in terms of the dissociation energy of the dimer ion. 相似文献
5.
《Radiation Physics and Chemistry》2008,77(9):1009-1020
The effects of pH and dissolved O2 on the γ-radiolysis of water were studied at an absorbed dose rate of 2.5 Gy s−1. Argon- or air-saturated water with no headspace was irradiated and the aqueous samples were analyzed for molecular radiolysis products (H2 and H2O2) as a function of irradiation time. The experimental results were compared with computer simulation results using a comprehensive water-radiolysis kinetic model, consisting of the primary radiolysis production, subsequent reactions and related acid–base equilibria. Both the experimental and computer model results were discussed based on the steady-state kinetic analysis of smaller reaction sets consisting of key production and removal reactions. While the main production path for a water decomposition product is the primary radiolysis, the main removal path varies. For H2O2 the main removal path is the reactions with eaq− and OH, whereas for H2 it is the reaction with OH. As a result, the presence of a dissolved species, or a change in chemical environment, affects the concentrations of H2O2 and H2 through interaction with radicals eaq− and OH. Over a wide range of conditions, there exist quantitative but simple relationships between the radical and the molecular product concentrations. The experimental and model analyses show that dissolved oxygen increases the steady-state concentrations of H2O2 and H2 by reacting with OH and eaq–, and the impact of oxygen is more noticeable at pH below 8. The steady-state concentrations of water decomposition products are nearly independent of pH in the range 5–8. However, raising pH above the pKa value of the acid–base equilibrium of H (⇆eaq−+H+) significantly increases [H2O2] and [H2] at the expenses of [OH] and [eaq–]. At pH >10, the radiolytical production of O2 becomes significant, but at a finite rate. This considerably increases the time for the irradiated system to reach a steady state, and is responsible for different impacts on [H2O2] and [H2] due to radically produced O2, compared to impacts due to initially dissolved O2. Model sensitivity analysis has shown that at higher pHs (pH >10) transient species such as O2− and O3− play a major role in determining the steady-state concentration of molecular products H2 and H2O2. Further validation of the water radiolysis model, particularly at higher pHs, is also discussed. 相似文献
6.
Kravchenko E. A. Kargin Yu. F. Egorysheva A. V. Buslaev Yu. A. 《Russian Journal of Coordination Chemistry》2001,27(8):542-547
It was earlier found from nuclear quadrupole resonance (NQR) measurements and computer modeling that -Bi2O3, Bi3O4Br and mixed oxides Bi2O3· 2Al2O3, Bi2O3· 2Ga2O3, Bi2O3· 3GeO2, and 2Bi2O3· 3GeO2exhibit local ordered magnetic fields from 30 to 200 G. It thus follows that these compounds are not diamagnets in a conventional sence of the word. With the aim of revealing previously unknown magnetic properties in bismuth(III) oxide-based Main Group element compounds, the mixed bismuth–boron oxides 2Bi2O3· B2O3, 3Bi2O3· 5B2O3, and Bi2O3· 3B2O3were prepared and studied using 209Bi NQR. The quadrupole interactions of the 209Bi nuclei and their electronic environment were studied, the crystallochemical features of the compounds were discussed, and the conformity of the 209Bi results to the X-ray structure data was verified. The preliminary tests in the field of a permanent magnet showed that the resonance intensities increase in external magnetic fields, indicating that a magnetism of unknown nature develops in the titled compounds. It was found reasonable to continue studies of the magnetic properties of these compounds using single-crystal 209Bi NQR in external magnetic fields. 相似文献
7.
The apparent molar volumes and adiabatic compressibilities of 18-Crown-6, 15-Crown-5, 12-Crown-4, tetraglyme, and triglyme were measured at 25°C in H2O and D2O. The contribution of the -CH2CH2O- group to the limiting partial molar volumes and compressibilities of cyclic and open-chain ethers in both solvents are compared and solvent isotope effects calculated. It is concluded, based on the compressibility results, that there is a subtle difference between the hydration of the ethene oxde group in cyclic and open-chain ethers and that this difference persists in D2O. These results indicate that the calculation of limiting apparent molar compressibilities using additivity schemes will have to account for whether the group is in a cyclic or open-chain compound. 相似文献
8.
Da-Zhi Li Lin-Yan Feng Ling Pei Ming-Zhi Song Li-Juan Zhang Hui Wang Hua-Jin Zhai 《International journal of quantum chemistry》2019,119(15):e25907
Boron oxide clusters are electron-deficient species with novel structures and bonding, in which the emergence of rhombic and boroxol rings is of interest. We report on computational prediction of the global-minimum structures for two boron oxide clusters: B4O5 and B4O5−. These structures differ distinctly, as established through global machine searches and electronic structure calculations at B3LYP and single-point CCSD(T) levels. While B4O5 neutral cluster has a rhombic B2O2 core, the B4O5− anion features a boroxol B3O3 ring. One electron completely changes the potential landscapes. Bonding analyses show that the 4π electron-counting is crucial for a rhombic B O cluster, in contrast to π sextet for a boroxol ring, which underlies the competition between rhombic and boroxol rings in B4O5/B4O5− clusters. A possible pathway for rhombic-to-hexagonal transformation is proposed based on intrinsic reaction coordinate calculations. Anion B4O5− cluster, a new member of the inorganic benzene family, is among the smallest B O species with a free-standing boroxol ring, governed collectively by composition and electron-counting. 相似文献
9.
Reactions of carboxylic acids with lead play an important role in the atmospheric corrosion of lead and lead-tin alloys. This is of particular concern for the preservation of lead-based cultural objects, including historic lead-tin alloy organ pipes. Two initial corrosion products, Pb(3)O(2)(CH(3)COO)(2)·0.5H(2)O (1) and Pb(2)O(HCOO)(2) (2), had been identified through powder diffraction fingerprints in the Powder Diffraction File, but their structures had never been determined. We have crystallized both compounds using hydrothermal solution conditions, and structures were determined using laboratory and synchrotron single-crystal X-ray diffraction data. Compound 1 crystallizes in P1, and 2 in Cccm. These compounds may be viewed as inorganic-organic networks containing single and double chains of edge-sharing Pb(4)O tetrahedra and have structural similarities to inorganic basic lead compounds. Bond valence sum analysis has been applied to the hemidirected lead coordination environments in each compound. Atmospheric exposure experiments contribute to understanding of the potential for conversion of these short-term corrosion products to hydrocerussite, Pb(3)(CO(3))(2)(OH)(2), previously identified as a long-term corrosion product on lead-rich objects. Each compound was also characterized by elemental analysis, thermogravimetric analysis and differential scanning calorimetry (TGA-DSC), and Raman spectroscopy. 相似文献
10.
Introduction 2MgO·B2 O3(Mg2 B2 O5)and 2MgO·B2 O3·H2 Omightbepreparedaswhiskermaterials .12MgO·B2 O3·H2 OnamedszaibelyiteisamagnesiumboratemineralwithastructuralformulaofMg2 [B2 O4 (OH) 2 ].2 Itisdifficulttosynthesizethiscompoundinthelaboratory .Recently ,weobtainedasimilarcompound 2MgO·B2 O3·1 5H2 Owhenwetriedtopreparewhiskerof 2MgO·B2 O3·H2 Obythephasetransformationof 2MgO·2B2 O3·MgCl2 ·14H2 OinH3BO3solutionunderhydrothermalcondition .Itishope fultopreparewh… 相似文献
11.
M. Harcharras A. Ennaciri N. Khay K. Brouzi 《Phosphorus, sulfur, and silicon and the related elements》2013,188(6):1247-1254
The thermal dehydration of Mg 2 P 2 O 7 ·; 6H 2 O were studied, in the range 25-800°;C, by thermogravimetric analysis (TG-DSC), x-ray diffraction, and infrared spectroscopy. According to the TG-DSC curves, the dehydration of this salt takes place in two stages. The results of thermal analysis, x-ray patterns, and infrared spectra of this compound heated at different temperatures showed that, after dehydration, Mg 2 P 2 O 7 ·; 6H 2 O decomposes into dihydrate Mg 2 P 2 O 7 ·; 2H 2 O diphosphate then to an amorphous Mg 2 P 2 O 7 product which crystallises at 665°;C to give anhydrous diphosphate f Mg 2 P 2 O 7 . The j H enthalpy of the dehydration of Mg 2 P 2 O 7 ·; 6H 2 O and of the formation of f Mg 2 P 2 O 7 have been calculated from thermogravimetric data. The infrared spectroscopic study of Mg 2 P 2 O 7 ·; 6H 2 O and of its heated products, reveals the existence of the characteristic bands of the P 2 O 7 group ( x as POP and x s POP) and showed that the POP angle is bent in these salts. In these compounds, the POP angle values are estimated using the Lazarev's relationship. 相似文献
12.
《Journal of solid state chemistry》1987,71(1):103-108
A systematic study of compound and solid-solution formation in the system Li2ONb2O5TiO2 has been made. Several solid-solution series, based on LiNbO3, LiNb3O8, Li2Nb28O71, Li2TiO3, phase M, Li2Ti3O7, and TiO2, have been characterized. In all cases, the principal solid-solution mechanism appears to involve stoichiometric formulae with constant overall cation content. One new phase, of approximate formula Li13TiNb5O21, has been prepared. A subsolidus phase diagram for the ternary system is presented. 相似文献
13.
Shilov G. V. Nikitina Z. K. Dobrovolskii Yu. A. Leonova L. S. Chernyak A. V. Tarasov V. P. Atovmyan L. O. 《Russian Journal of Coordination Chemistry》2004,30(11):759-764
Single crystals of the Rb4H2I2O10· 4H2O were synthesized for the first time and studied by X-ray diffraction analysis. The crystals are monoclinic, a = 7.321(6) Å, b = 12.599(8) Å, c = 8.198(8) Å, = 96.30(7)°, Z = 2, space group P21/c. The H2I2O10
4– anion is formed by the edge-sharing IO6 octahedra. The anions are united by hydrogen bonds into a chain running along the x axis. The chains are combined by water molecules into a three-dimensional structure through hydrogen bonds. The compound is a proton conductor. The conductivity values measured at 20–60°C vary within 10–6 to 10–4 ohm–1 cm–1. 相似文献
14.
In-Jin Shon Hyun-Su Kang Jung-Mann Doh Jin-Kook Yoon 《Research on Chemical Intermediates》2014,40(7):2407-2413
Rapid sintering of nanostructured 2MgAl2O4–MgAl2Ti3O10 composite in a pulsed current activated sintering process was investigated. The advantage of this process is that it enables very rapid densification to near theoretical density and prevents grain growth in nanostructured materials. Highly dense nanostructured 2MgAl2O4–MgAl2Ti3O10 composite was produced by simultaneous application of 80 MPa pressure and a pulsed current of 2,800 A for 2 min. The sintering behavior, grain size, and mechanical properties of the 2MgAl2O4–MgAl2Ti3O10 composite were investigated. 相似文献
15.
《Chemical physics letters》1985,115(3):268-274
A molecular-orbital study, performed using both multiple scattering Xα and ab initio SCF models, is reported for the protonation process of O2, O2− and O22−. The main features of both molecular electrostatic potential and electron deformation density contour maps are compared and discussed. 相似文献
16.
S. V. Larionov L. I. Myachina L. A. Glinskaya I. V. Korol’kov E. M. Uskov O. V. Antonova V. M. Karpov V. E. Platonov V. P. Fadeeva 《Russian Journal of Coordination Chemistry》2012,38(12):717-723
Compounds p-HOOCC6F4COOH · H2O (H2L · H2O), [Tb2(H2O)4(L)3 · 2H2O] n (I), and Tb2(Phen)2(L)3 · 2H2O (II) are synthesized. According to the X-ray structure analysis data, the crystal structure of H2L · H2O is built of centrosymmetric molecules H2L and molecules of water of crystallization. The crystal structure of compound I is built of layers of coordination 2D polymer [Tb2(H2O)4(L)3] n and molecules of water of crystallization. The ligands are the L2? anions performing both the tetradentate bridging and pentadentate bridging-chelating functions. The coordination polyhedron TbO9 is a distorted three-capped trigonal prism. Acid H2L manifests photoluminescence in the UV region (??max = 368 nm). Compounds I and II have the green luminescence characteristic of the Tb3+ ions, and the band with ??max = 545 nm (transition 5 D 4?? 7 F 5) is maximum in intensity. The photoluminescence intensity of compound II is higher than that for compound I. 相似文献
17.
《Journal of solid state chemistry》1987,66(2):256-262
By means of X-ray phase analysis, IR spectroscopy, and DTA, the system 2TeO2 · V2O5Li2O · V2O5 · 2TeO2 was investigated and its phase diagram was constructed. The formation of a new compound with composition Li2O · 3V2O5 · 6TeO2, melting incongruently was documented. A comparison of the bands in the IR spectrum was made. Stable glasses in the whole range of concentrations were prepared. From the IR spectra of the glasses, the corresponding crystallization products, and the data of known crystal structures, a model of the short-range order in the glasses was proposed. 相似文献
18.
Glasses with compositions 60Bi2O3–(40?x)B2O3–xGa2O3 (x = 5, 10, 15, 20 mol%) are prepared by conventional melting method. The thermal properties are investigated by differential thermal analysis (DTA) and the structures of the glasses were probed by Infrared, Raman and X-ray photoelectron spectroscopy (XPS). The results show that density, refractive index and optical basicity increase with the increase of Ga2O3. The glass transition temperature (Tg), the onset crystallization temperature (Tx), ΔT (Tx?Tg) decrease with the content of Ga2O3. The cut-off edges in ultraviolet and infrared shift to longer wavelength with the increase of Ga2O3. On the other hand, the addition of Ga2O3 causes a progressive coordination number change of the boron atom from 3 to 4. XPS result indicates both Bi5+ and Bi3+ exist in 5 mol% Ga2O3 content, while Bi5+ amounts decrease with the increase of Ga2O3 contents. The glass is mainly composed of [BiO6], [BO3], [BO4] and [GaO4] polyhedra. Glasses are supposed to have layer structure. [BO3] triangle and [BO4] tetrahedra may be located between the [GaO4] tetrahedral and [BiO6] octahedra to prevent crystallization and to compensate electric charge. 相似文献
19.
《Fluid Phase Equilibria》2002,193(1-2):229-243
A thermodynamic model was established to determine ion-exchange conditions for the synthesis of potassium hexatitanate (K2O·6TiO2) and titanium dioxide (TiO2) from potassium tetratitanate (K2O·4TiO2) fiber. In the proposed model equilibrium species in the solid phase and corresponding ion-exchange equilibrium constants at 298.15 K were determined from the experimental data of Sasaki et al. [Inorg. Chem. 24 (1985) 2265]. In order to verify the proposed model, prediction results were compared with experimental data determined in literature and those measured in this work. The comparison shows a good agreement. Based on this, the proposed model was also used to predict more extensive suitable conditions for the synthesis of K2O·6TiO2 and TiO2. 相似文献
20.
L. B. Serezhkina E. V. Peresypkina Ya. A. Medvedkov A. V. Virovets V. N. Serezhkin 《Russian Journal of Inorganic Chemistry》2013,58(12):1465-1469
Cs2[(UO2)2(C2O4)3] (I) and Cs2[UO2(C3H2O4)2] · H2O (II) have been synthesized and studied by X-ray diffraction. The crystals of complexes I and II are monoclinic: a = 8.1453(2) Å, b = 8.9831(2) Å, c = 11.3897(4) Å, β = 104.0950(10)°, V = 808.29(4) Å3, space group P21/n, Z = 2, and R 1 = 0.0255 for I and a = 9.6998(2) Å, b = 17.8686(3) Å, c = 8.2074(2) Å, β = 97.5780(10)°, V = 1410.10(5) Å3, space group P21/c, Z = 4, and R 1 = 0.0287 for II. The uranium-containing structural units of complexes I and II are [(UO2)2(C2O4)3]2? chains and [UO2(C3H2O4)2] 2 4? dimers, which belong to the AK 0.5 02 T11 and AT11B01 crystallochemical groups (A = UO 2 2+ , K02 and T11 = C2O 4 2? , T11 and B01 = C3H2O 4 2? ) of uranyl complexes. 相似文献