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101.
A. A. Soliman 《Journal of Thermal Analysis and Calorimetry》2007,89(2):389-392
A brief derivation of the Kissinger’s equation for analysis of experimental data of non-isothermal glass transition peaks
based on the free volume model is given. This equation was applied successfully to Cu0.3(SSe20)0.7 chalcogenide glass for different heating rates. For granted this model, the obtained glass transition activation energy,
E
g must be constant throughout the whole glass transition temperature range. This required that T
g to be determined for three characteristic temperature points for each DSC curve. 相似文献
102.
K. Stwe 《无机化学与普通化学杂志》1996,622(8):1423-1427
Contributions to the Crystal Chemistry of Uranium Tellurides. II. The Crystal Structure of Diuranium Pentatelluride U2Te5 Via chemical transport reactions with TeBr4 as transporting agent single crystals of the title compound up to a size of 5 mm were available from the elements. The analysis by atomic emission spectrometry gave UTe2.52(4). By X-ray single crystal structure analysis we found that U2Te5 crystallizes monoclinic (space group C2/m, Z = 4) with a = 3443.3(5) pm, b = 418.65(3) pm, c = 607.97(6) pm and β = 95.35(1)º in a new structure type. The layer structure is built up by bicapped trigonal prisms, one half as isolated building units, the other connected via faces as fourfold capped biprisms. A structural relationship of diuranium pentatelluride to the adjacent phases in the phase diagram U? Te can be expressed by the formulation as UTe2 · UTe3. 相似文献
103.
The reactions of HgE (E=S, Se) with HgX2 and MX4 (M=Zr, Hf; X=Cl, Br) in evacuated glass ampoules lead to a series of isotypic compounds of the general formula Hg3E2[MX6] in the form of colorless (X=Cl) and light-yellow (X=Br) air-sensitive crystals. The crystal structures of Hg3S2[ZrCl6] (I), Hg3S2[HfCl6] (II), Hg3Se2[ZrCl6] (III), Hg3Se2[HfCl6] (IV), Hg3S2[ZrBr6] (V), and Hg3Se2[ZrBr6] (VI) were refined based on single-crystal data. All compounds crystallize in the monoclinic space group P21/a with the lattice parameters a=662.18(2) pm, b=734.97(3) pm, c=1290.83(5) pm, β=91.755(2)° for (I) and and a=701.97(3) pm, b=756.79(3) pm, c=1350.99(6) pm, β=92.164(3)° for (VI). The structures are built of (Hg3E2)2+ layers stacked perpendicular to the c-axis. The polycationic layers consist of two-dimensionally linked 12-membered Hg6E6 rings in the chair conformation with linear coordinated Hg and trigonal pyramidal coordinated chalcogen atoms. Almost regular octahedral [MX6]2− ions are embedded between the layers. This arrangement is closely related to the structure of Hg3S2[SiF6], which represents a higher symmetric congener. The structure relation is discussed using the supergroup-subgroup relation between space groups. 相似文献
104.
M. I. Avramov D. M. Petrović S. R. Lukić S. J. Skuban 《Journal of Thermal Analysis and Calorimetry》1995,44(5):1203-1209
Results of thermal investigations of the amorphous five-component chalcogenide system Ge20As14(SexS1?x)52I14 are presented. Differential thermal analysis (DTA), derivative differential thermal analysis (DDTA), and dilatometry were employed to determine the temperatures of softening and partial crystallization of the samples. Thermal treatment of the samples at 1000°C and recording of the corresponding thermogravimetric (TG) and derivative thermogravimetric (DTG) curves allowed an elucidation of the full mechanism of their decomposition, which proceeds via seven characteristic phase transitions. 相似文献
105.
Whereas reaction of [PhCH2NMe3]2|Te6Fe8(CO)24] (1) in refluxing CH2CI2 forms Fe2(CO)6(μ0-) TeCH2Te), treatment of 1 with Ph2SnCl 2 or Mel gave the oxidation product Te2Fe3(CO)9. Oxidation of 1 with [Cu(CH3CN)4]BF4 afforded Te2Fe3(CO)9 in good yield. Cluster 1 was converted to [PhCH2NMe3][Te4Fe5(CO)14] (2) in MeOH/CH2Cl2 solution. Cluster 2 was structurally characterized by single-crystal X-ray diffraction and spectral methods. Complex 2 is composed of two Te2Fe2(CO)6 fragments linked by one Fe(CO)2 group. 2 crystallizes in the orthorhombic space group Pbcn with a = 13.351 (4) Å, b = 13.417 (4) Å, c = 26.077 (3) Å, V = 4671 (2) Å 3, Z = 4. 相似文献
106.
Megan M. Treece Jordan C. Kelly Kate E. Rosello Andrew J. Craig Jennifer A. Aitken 《Acta Crystallographica. Section C, Structural Chemistry》2023,79(9):353-364
Our calculations of the global instability index (G) values for some diamond-like materials with the general formula I2–II–IV–VI4 have indicated that the structures may be unstable or incorrectly determined. To compute the G value of a given compound, the bond valence sums (BVSs) must first be calculated using a crystal structure. Two examples of compounds with high G values, based on data from the literature, are the wurtz–stannite-type dicopper cadmium silicon tetrasulfide (Cu2CdSiS4) and the stannite-type dicopper mercury tin tetrasulfide (Cu2HgSnS4), which were first reported in 1967 and 1965, respectively. In the present study, Cu2CdSiS4 and Cu2HgSnS4 were prepared by solid-state synthesis at 1000 and 900 °C, respectively. The phase purity was assessed by powder X-ray diffraction. Optical diffuse reflectance UV/Vis/NIR spectroscopy was used to estimate the optical bandgaps of 2.52 and 0.83 eV for Cu2CdSiS4 and Cu2HgSnS4, respectively. The structures were solved and refined using single-crystal X-ray diffraction data. The structure type of Cu2CdSiS4 was confirmed, where Cd2+, Si4+ and two of the three crystallographically unique S2− ions lie on a mirror plane. The structure type of Cu2HgSnS4 was also verified, where all ions lie on special positions. The S2− ion resides on a mirror plane, the Cu+ ion is situated on a fourfold rotary inversion axis and both the Hg2+ and the Sn4+ ions are located on the intersection of a fourfold rotary inversion axis, a mirror plane and a twofold rotation axis. Using the crystal structures solved and refined here, the G values were reassessed and found to be in the range that indicates reasonable strain for a stable crystal structure. This work, together with some examples gathered from the literature, shows that accurate data collected on modern instrumentation should be used to reliably calculate BVSs and G values. 相似文献
107.
A multifunctional three-dimensional quaternary chalcogenide [Na5Zn3.5Sn3.5S13]·6H2O has been synthesized by solvothermal reactions. [Na5Zn3.5Sn3.5S13]·6H2O represents an interesting example of metal chalcogenides that combines semiconductivity, porosity, and light emission in a single structure. It crystallizes in the cubic space group Fm-3c, a=17.8630(3) Å, V=5699.85(17) Å3, Z=8. The compound decomposes at ∼450 °C. A band gap of 2.9 eV is estimated from the optical diffuse reflectance data. A strong photoluminescence peak is observed at 2.43 eV in Mn doped samples. The electronic and optical properties of this compound can be systematically tuned by substitution of metal and chalcogen elements. 相似文献
108.
A. L. Gushchin M. N. Sokolov D. Yu. Naumov V. P. Fedin 《Journal of Structural Chemistry》2008,49(4):748-752
By the reaction of [Mo3S4(C2O4)3(H2O)3]2− with PdCl2 and NH4H2PO2 as a reducing agent, followed by the addition of PPh3, a new oxalate cuboidal cluster complex [Mo3(PdPPh3)S4(C2O4)3(H2O)3]2− is obtained. It was isolated and structurally characterized as K2[Mo3(PdPPh3)S4(C2O4)3(H2O)3]·0.5H2O.
Original Russian Text Copyright ? 2008 by A. L. Gushchin, M. N. Sokolov, D. Yu. Naumov, and V. P. Fedin
__________
Translated from Zhurnal Strukturnoi Khimii, Vol. 49, No. 4, pp. 775–778, May–June, 2008. 相似文献
109.
The pressure dependence of the electrical resistivity of bulk GeSe2 glass shows a semiconductor-to-metal transition at 7 GPa pressure. The high pressure phase is examined using the x-ray diffractometer
and is found to be crystalline, with a face-centred cubic structure havinga = 4·06 A. The electrical conductivity has also been studied as a function of temperature at various pressures. 相似文献
110.
Different
methods have been used by various workers to determine the activation energy
of thermal crystallization (Ec)
in chalcogenide glasses using non-isothermal DSC data. In the present work,
the crystallization kinetics of two important binary alloys Se80Te20
and Se80In20 is studied using
non-isothermal DSC data. DSC scans of these alloys have been taken at five
different heating rates. The values of activation energy of crystallization
(Ec) have been determined
by four different methods, i.e., Kissinger's method, Matusita-Sakka
method, Augis-Bennett's method and Ozawa's method, have
been used to calculate Ec.
The results obtained have been compared with each other to see the effect
of using different methods in the determination of Ec. 相似文献