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1.
The molecular constants of LnF (Ln = Ce?Lu) for the ground state have been estimated based on the available spectroscopic characteristics of lanthanum and lanthanide monofluorides. These constants have been used for calculating the reduced Gibbs energy (?[G 0(T) ? H 0(0)]/T) of the compounds in the ideal gas state in the range 298.15–3000 K at the standard pressure p 0 = 0.1 MPa. The rigid rotator-harmonic oscillator approximation with additional inclusion of the anharmonicity of oscillations (by the method of Mayer and Goeppert-Mayer) and correction for centrifugal stretching have been used. The contribution made by electronic excitation has been calculated by two methods: based on the energies of the excited states of molecules and based on the electronic excitation energy of the free Ln+ ion. Analogous data are reported for lanthanide monochlorides.  相似文献   

2.
The heat capacities of Pb2V2O7 and Pb3(VO4)2 as a function of temperature in the range 350–965 K have been studied by the differential scanning calorimetry method. The CP = f(T) curve for Pb2V2O7 is described by the equation Cp = (230.76 ± 0.51) + (73.60 ± 0.50)×10-3T ? (18.38 ± 0.54)×105T-2 in the entire temperature range. For Pb3(VO4)2, there is a well-pronounced extreme point in the CP = f(T) curve at T = 371.5 K, which is caused by the existence of a structural phase transition. The thermodynamic properties of the oxide compounds have been calculated.  相似文献   

3.
The temperature dependence of the heat capacity C p o of the [(Me3Si)7C60]2 fullerene complex was measured for the first time using precision adiabatic vacuum calorimetry over the temperature range 6.7–340 K and high-accuracy differential scanning calorimetry at 320–635 K. For the most part, the error in the C p o values was about ±0.5%. An irreversible endothermic effect caused by the splitting of the dimeric bond between fullerene fragments and the thermal decomposition of the complex was observed at 448–570 K. The thermodynamic characteristics of this transformation were calculated and analyzed. Multifractal analysis of the low-temperature (T < 50 K) heat capacity was performed, and conclusions were drawn concerning the character of the heterodynamicity of the structure. The experimental data obtained were used to calculate the standard thermodynamic functions C p o (T), H o (T) ? H o (0), S o (T) ? S o (0), and G o (T) ? H o (0) over the temperature range from T → 0 to 445 K and estimate the standard entropy of formation of the compound from simple substances at 298.15 K. The standard thermodynamic properties of [(Me3Si)7C60]2 are compared with those of the (C60)2 dimer, the [(η6-Ph2)2Cr]+[C60]?? fulleride, and the initial C60 fullerene.  相似文献   

4.
The temperature dependence of the heat capacity of a first-generation liquid crystal carbosilane dendrimer with methoxyphenyl benzoate end groups is studied for the first time in the region of 6–370 K by means of precision adiabatic vacuum calorimetry. Physical transformations are observed in this interval of temperatures, and their standard thermodynamic characteristics are determined and discussed. Standard thermodynamic functions Cp°(T), H°(T) ? H°(0), S°(T) ? S°(0), and G°(T) ? H°(0) are calculated from the obtained experimental data for the region of Т → 0 to 370 K. The standard entropy of formation of the dendrimer in the partially crystalline state at Т = 298.15 K is calculated, and the standard entropy of the hypothetic reaction of its synthesis at this temperature is estimated. The thermodynamic properties of the studied dendrimer are compared to those of second- and fourth-generation liquid crystal carbosilane dendrimers with the same end groups studied earlier.  相似文献   

5.
The results of measurement of equilibrium constants of 30 reactions involving lanthanum and lanthanide fluorides (LnF, LnF2, and LnF3) and 14 reactions involving lanthanum and lanthanide monochlorides (Ln = La-Lu) have been summarized. These constants have been used for calculating the enthalpies of reactions by the second and third laws, from which the enthalpies of atomization Δat H 0 0 of LnCl, LnF, and LnF2 have been determined. Comparison of the calculation results shows that the thermodynamic functions of LnCl and LnF (Ln = Ce-Yb) in which the electronic excitation contribution has been calculated from the excitation energies of Ln+ ions allow one to adequately determined the Δat H 0 0 values from experimental data. Using the trends in the change in Δat H 0 0 as a function of the atomic number of a lanthanide, the enthalpies of atomization of compounds for which experimental data are lacking have been estimated. The Δat H 0 0 values for LnCl+ ions have been calculated. The reliability of the Δat H 0 0 values for LnF+ ions have been assessed.  相似文献   

6.
The temperature dependence of the heat capacity of triphenylantimony dibenzoate Ph3Sb(OC(O)Ph)2 is studied in the range of 6–480 K by means of precision adiabatic vacuum calorimetry and differential scanning calorimetry. The melting of the compound is observed in this temperature range, and its standard thermodynamic characteristics are identified and analyzed. Ph3Sb(OC(O)Ph)2 is obtained in a metastable amorphous state in a calorimeter. The standard thermodynamic functions of Ph3Sb(OC(O)Ph)2 in the crystalline and liquid states are calculated from the obtained experimental data: Cp°(T), H°(T)–H°(0), S°(T), and G°(T)–H°(0) for the region from T → 0 to 480 K. The standard entropy of formation of the compound in the crystalline state at T = 298.15 K is determined. Multifractal processing of the low-temperature (T < 50 K) heat capacity of the compound is performed. It is concluded that the structure of the compound has a planar chain topology.  相似文献   

7.
The heat capacities of first- and third-generation carbosilane dendrimers with terminal phenyldioxolane groups are studied as a function of temperature via vacuum and differential scanning calorimetry in the range of 6 to 520 K. Physical transformations that occur in the above temperature range are detected and their standard thermodynamic characteristics are determined and analyzed. Standard thermodynamic functions Cpο(T), [H°(T) ? H°(0)], [S°(T) ? S°(0)], and [G°(T) ? H°(0)] in the temperature range of T → 0 to 520 K for different physical states and the standard entropies of formation of the studied dendrimers at T = 298.15 K are calculated, based on the obtained experimental data.  相似文献   

8.
Equilibrium geometric parameters, normal mode frequencies and intensities in IR spectra, atomization enthalpy, and relative energies of low-lying electronic states of scandium fluoride molecules (ScF, ScF2, and ScF3) are calculated by the coupled-cluster method (CCSD(T)) in triple-, quadruple, and quintuple-zeta basis sets with the subsequent extrapolation of the calculation results to the complete basis set limit. The ScF molecule is also studied by the CCSDT technique. The error in the approximate calculation of triple excitations in the CCSD(T) method does not exceed 0.002 Å for the equilibrium internuclear distance R e, 4 cm?1 for the vibrational frequency, and 0.2 kcal/mol for the dissociation energy of the molecule. In the ground electronic state \(\tilde X^2 \) A 1(C 2ν ) of ScF2 molecules, R e(Sc-F) = 1.827 Å and αe(F-Sc-F) = 124.2°; the energy barrier to bending (linearization) h = E min(D g8h ) ? E min(C) = 1652 cm?1. The relative energies of Ã2Δ g and \(\tilde B^2 \)Π g electronic states are 3522 cm?1 and 14633 cm?1 respectively. The bond distance in the ScF3 molecule (\(\tilde X^1 \) A1, D 3h ) is refined: R e(Sc-F) = 1.842 Å. The atomization enthalpies Δat H 298 0 of ScF k molecules are 139.9 kcal/mol, 289.0 kcal/mol, and 444.8 kcal/mol for k = 1, 2, 3 respectively.  相似文献   

9.
Heterometallic pivalate Co2Sm(Piv)7(2,4-Lut)2 (1) was prepared for the first time and structurally characterized at 293 and 160 K. Antiferromagnetic exchange interactions are dominant in complex 1. This compound experiences a first-order phase transition within 210–260 K. A set of thermodynamic functions was obtained for this complex (C p , H T 0 - H 180 0 , and S T 0 ), and parameters were determined for solid-phase thermolysis where samarium cobaltate SmCoO3 is the only product.  相似文献   

10.
The values of ΔH°298, S°298, H°298H°0, T, ΔH fus, and C p(T), as well as the temperature dependences of the Gibbs energy function, are calculated for Bi8O11 oxide by proven computational methods.  相似文献   

11.
The low-temperature heat capacity of Na2Lu (MoO4)(PO4) was measured by adiabatic calorimetry in the range of 7.47–345.74 K. The experimental data were used to calculate the thermodynamic functions of Na2Lu (MoO4)(PO4). At 298.15 K, the following values were obtained: C p 0 (298.15 K) = 237.7 ± 0.1 J/(K mol), S 0(298.15 K) = 278.1 ± 0.8 J/(K mol), H 0(298.15 K) ? H 0 (0 K) = 42330 ± 20 J/mol, and Φ0(298.15 K) = 136.1 ± 0. 3 J/(K mol). A heat capacity anomaly was found in the range of 10-67 K with a maximum at T tr = 39.18 K. The entropy and enthalpy of transition are ΔS = 12.39 ± 0.75 J/(K mol) and ΔH = 403 ± 16 J/mol. The thermal investigation of sodium lutetium molybdate phosphate in the high-temperature range (623–1223 K) was performed using differential scanning calorimetry. It was found that during melting in the range of 1030–1200 K, Na2Lu(MoO4)(PO4) degrades to simpler compounds; the degradation scenario is verified by X-ray powder diffraction.  相似文献   

12.
The subsolidus region of the Ag2MoO4-MgMoO4-Al2(MoO4)3 ternary salt system has been studied by X-ray phase analysis. The formation of new compounds Ag1 ? x Mg1 ? x Al1 + x (MoO4)3 (0 ≤ x ≤ 0.4) and AgMg3Al(MoO4)5 has been determined. The Ag1 ? x Mg1 ? x Al1 + x (MoO4)3 variable-composition phase is related to the NASICON type structure (space group R \(\bar 3\) c). AgMg3Al(MoO4)5 is isostructural to sodium magnesium indium molybdate of the same formula unit and crystallizes in triclinic system (space group P \(\bar 1\), Z = 2) with the following unit cell parameters: a = 9.295(7) Å, b = 17.619(2) Å, c = 6.8570(7) Å, α = 87.420(9)°, β = 101.109(9)°, γ = 91.847(9)°. The compounds Ag1 ? x Mg1 ? x Al1 + x (MoO4)3 and AgMg3Al(MoO4)5 are thermally stable up to 790 and 820°C, respectively.  相似文献   

13.
Tellurite of the composition Li2CeTeO5 is synthesized by solid-phase method from cerium(IV) and tellurium(IV) oxides and lithium carbonate. The type of syngony, the unit cell parameters, and the compound’s X-ray and pycnometry densities are determined via X-ray diffraction analysis. The isobaric heat capacity of lithium–cerium tellurite is studied by means of dynamic calorimetry in the temperature range of 298.15–673 K; the results serve as the basis for deriving C p ° ~ f(T) dependency equations and determining the compound’s thermodynamic functions. λ-shaped anomalous effects, due probably to Type II phase transitions, are found on the C p ° ~ f(T) dependence.  相似文献   

14.
(U)PBE0/cc-pVDZ method is used to study the structure of C60Cl30, C60(OH)30 molecules and Fe@C60(OH)30 endocomplex. The triplet state of the endocomplex is shown to be the lowest in energy among its four states corresponding to different spin multiplicities and positions of Fe nucleus within the fullerene cavity. This state is characterized by bonding between the iron atom and one of two benzenoid cycles of the carbon cage, six internuclear Fe–C distances (208 pm), and 1s22s22p63s23p63d7.24s0.14p0.3 electron configuration of iron with spin population of 2.36.  相似文献   

15.
A ternary salt system Rb2MoO4-Eu2(MoO4)3-Hf(MoO4)2 was studied in the subsolidus area by X-ray phase analysis. A novel ternary molybdate, Rb4.98Eu0.86Hf1.11(MoO4)6, formed in the system. The Rb4.98Eu0.86Hf1.11(MoO4)6 rubidium-europium-hafnium molybdate crystals were grown by solution-melt crystallization under the spontaneous nucleation conditions. The structure and composition of this compound were refined by single crystal X-ray diffraction (X8 APEX automated diffractometer, MoK α radiation, 1753 F(hkl), R = 0.0183). The crystals are trigonal, a = b = 10.7264(1) Å, c = 38.6130(8) Å, V = 3847.44(9) Å3, Z = 6, space group R \(\bar 3\) c. The three-dimensional mixed framework of the structure comprises Mo tetrahedra and two types of octahedra, (Eu,Hf)O6 and HfO6. The large cavities of the framework include two types of the rubidium atom. The distribution of the Eu3+ and Hf4+ cations over two crystallographic positions was refined.  相似文献   

16.
A novel Cu(II) complex Cu2(Endc)2(Bipy)2 has been synthesized by the reaction of Cu(NO3)2 · 3H2O, Endc (endo-norbornene-cis-5,6-dicarboxylic acid), and Bipy (2,2-bipyridine) at room temperature. Elemental analysis, IR spectra, and X-ray single-crystal diffraction were carried out to determine the composition and crystal structure. Crystal data for this complex: triclinic, P \(\bar 1\) with a = 9.0373(10), b = 10.1637(11), c = 10.5574(12) Å, α = 65.78(1)°, β = 72.32(2)°, β = 73.23(2)°, Z = 1, V = 827.46(16) Å3, ρ c = 2.160 g/cm3, F(000) = 410.0, R = 0.0483 and wR = 0.0958 independent reflections for 4468 observed ones (I > 2 σ(I)).The Cu2+ ion is coordinated by two nitrogen atoms from the Bipy molecule and three oxygen atoms from two Endc, giving a distorted squarepyramidal coordination geometry. Two neighboring Cu2+ ions are bridged by a pair of bimonodentate carboxyl groups of different Endc acids, giving a centrosymmetrical binuclear structure which a Cu…Cu distance of 3.2946 Å. The photoluminescence properties of the complex were studied at room temperature. The complex displays an obvious photoluminescent emission upon excitation at 390 nm in the solid state.  相似文献   

17.
The single crystals of [UO2(C2O4){CONH2N(CH3)2}2] were synthesized and studied by X-ray diffraction. The crystals are monoclinic, a = 7.461(2) Å, b = 8.828(2) Å, c = 11.756(2) Å, β = 107.21(3)°, space group Pc, Z = 2, R = 2.94%. The structure comprises infinite chains [UO2(C2O4){CONH2N(CH3)2}2] extended along [001] and corresponding to the AT11M 2 1 crystallochemical group (A = UO 2 2+ , T11 = C2O 4 2? , M1 = N,N-CONH2N(CH3)2) of uranyl complexes. The chains are connected into a three-dimensional framework by hydrogen bonds involving the oxygen atoms of oxalate and uranyl ions and the N,N-dimethylcarbamide methyl groups.  相似文献   

18.
A novel one-dimensional chain complex [Cd(NITpPy)2(N(CN)2)2)] n (NITpPy = 2-(4′-pyridyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide) has been synthesized and characterized structurally. It crystallizes in the triclinic space group P \(\bar 1\) with a = 7.1742(13), b = 9.4913(17), c = 13.208(2) Å, α = 71.020(2)°, β=87.308(2)°, γ = 70.503(2)°, V = 799.8(3) Å3, C28H32CdN12O4, Mr = 713.06, Z = 1, ρ c = 1.48 g/cm3, μ(MoK α) = 0.736 mm?1, F(000) = 364, R = 0.0275 and wR = 0.0605 for 2702 observed reflections with I > 2σ(I). The crystal structure consists of infinite chains of [Cd(NITpPy)2(N(CN)2)2)] units linked by dicyanamide anions [N(CN)2]?. Each Cd2+ ion is six-coordinated with the geometry of a distorted octahedron.  相似文献   

19.
Phase relationships in the subsolidus region of the system Na2MoO4-MnMoO4-Cr2(MoO4)3 were studied by means of X-ray diffraction and differential-thermal analyses. The possibility of obtaining a variablecomposition phase Na1?x Mn1?x Cr1+x (MoO4)3 (0 ≤ x ≤ 0.5) and ternary molybdate NaMn3Cr(MoO4)5 was examined. The temperature dependence of the conductivity of the phase Na1?x Mn1?x Cr1+x (MoO4)3 was analyzed.  相似文献   

20.
Rate constants for the two stages of germane dissociation (GeH4 → GeH2 + H2(I) and GeH2 → Ge + H2(II) have been derived from the studies of the chemiluminescence kinetics during germane dissociation in the presence of nitrous oxide behind shock waves at 1060–1300 K and the full density equal to ~10?5 mol/cm3. Analysis in terms of the RRKM model gave the following expressions for the rate constants of these reactions in the high and low pressure limits: k 1, ∞ = 2.0 × 1014exp(?208.0/RT) s?1; k 1, 0 = 1.7 × 1018(1000/T)3.85exp(?208.0/RT) cm3/(mol s); and k 2, 0 = 2.8 × 1015(1000/T)1.32exp(?135.0/RT) cm3/(mol s). The results, in combination with the available enthalpies of formation of radical GeH2, show that the back reaction for stage (I) has an energy barrier of about 66 kJ/mol.  相似文献   

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