Thermal properties of Na2TeO4(s) and TiTe3O8(s)

Molar heat capacity measurement on Na₂TeO₄(s) and TiTe₃O₈(s) were carried out using differential scanning calorimeter. The molar heat capacity values were least squares analyzed and the dependence of molar heat capacity with temperature for Na₂TeO₄(s) and TiTe₃O₈(s) can be given as, $$ \begin{gathered} {\text{C}}^{\text{o}}_{{{\text{p}},{\text{m}}}} \left\{ {{\text{Na}}_{ 2} {\text{TeO}}_{ 4} \left( {\text{s}} \right)} \right\} \,={159}.17 { } + 1.2\,\times\,10^{-4}T-{55}.34\,\times\,10^{5}/T^{2};\hfill \\ C^{\text{o}}_{{{\text{p}},{\text{m}}}} \left\{ {{\text{TiTe}}_{ 3} {\text{O}}_{ 8} \left( {\text{s}} \right)} \right\}\,=\,{ 275}.22{ }+{4}.0\,\times\, 10^{-5}T-{58}.28\,\times\,10^{5}/T^{2};\hfill \\ \end{gathered} $$ From this data, other thermodynamic functions were evaluated.     

Theoretical study of Na(4p2P) + Na(3s2S) and Cd(5p3P0) + Na(3s2S) collisions and their role in the energy transfer between Cd.* and Na

We have computed the cross sections for the energy transfer process Cd(5p³P₀) + Na(3s²S) → Cd(5s¹S) + Na(4p²P) and for the state changing collision Na(4p²P) + Na(3s²S) → Na(3d²D) + Na(3s²S), based on theoretical interaction potentials for the NaCd and Na2 systems, respectively. Our calculations shed light on the interpretation of experiments with laser excited Na+Cd vapour mixtures [1]. It turns out that Cd(5p³P₀), in rapid equilibrium with the doorway state Cd(5p³P₁), efficiently transfers energy to Na, populating the 4p²P state. The collisions with ground state Na cause a very fast conversion of the 4p³P₁ to the 3d²D state, from which the strongest emission is observed.     

Bis(crown ether)s as Na+-K+ ATPase model in a liquid membrane

A new type of bis(crown ether)s containing 15-crown-5 and monoaza-18-crown-6 actively transported Na⁺ and K⁺ in opposite directions across a dichloromethane membrane by pH control. The effect of the structure of the ion carriers on their transport abilities was examined. A key point for the molecular design of the carriers is how to give them complexing ability toward Na⁺ under acidic conditions. A proper choice of the transport conditions was found to be essential for the success of the double uphill transport.This paper is dedicated to the memory of the late Dr C. J. Pedersen.     

Chemisches Gleichgewicht der heterogenen Reaktion Na2SO3(aq) + Ca(OH)2(s) ⇌ 2NaOH(aq) + CaSO3(s)

Ohne Zusammenfassung     

Ca(1)(-)(x)Na(2)(x)Al(2)B(2)O(7): a structure with tunable density of Na(+) vacancies

A series of samples with the composition Ca(1)(-)(x)Na(2)(x)Al(2)B(2)O(7) (0 < x < or = 1) was investigated and a hexagonal structure with unusually large range of homogeneity (at least from x = 0.01 to 0.95) was revealed. The hexagonal phase consists of [Al(2)B(2)O(7)](infinity)(2)(-) lamellae stacked along the c axis, as in CaAl(2)B(2)O(7) and Na(2)Al(2)B(2)O(7). Nevertheless, the configuration and stacking sequence of the [Al(2)B(2)O(7)](infinity)(2)(-) lamellae are different in these three structures. In the hexagonal structure of Ca(1)(-)(x)()Na(2)(x)()Al(2)B(2)O(7), Ca and half Na cations (Na1) statistically occupy the same crystallographic site which is located between the [Al(2)B(2)O(7)](infinity)(2)(-) lamellae, the other half Na cations (Na2) distribute in the planes bisecting the [Al(2)B(2)O(7)](infinity)(2)(-) lamellae. Depending on the composition, the site occupation factor of Na2 site can vary in the same range as x, leading to a tunable density of Na(+) vacancies in the structure. The AlO(4) tetrahedra and BO(3) triangles in the structure tilt in appropriate ways to improve the bond valence sum of Na2 cations which are not sufficiently bonded to the anions.     

Metastable 11 K Superconductor Na(1-y)Fe(2-x)As(2)

The topochemical deintercalation of Na(+) ions from solid NaFeAs at room temperature in THF with iodine yields the superconducting phase Na(1-y)Fe(2-x)As(2) (T(c) ≈ 11 K). This metastable iron arsenide decomposes at 120 °C and is not accessible by high-temperature solid-state synthesis. X-ray powder diffraction confirms the ThCr(2)Si(2)-type structure, but reveals very small coherently scattering domains with a mean composition Na(0.9(2))Fe(1.7(1))As(2). HRTEM investigations show crystalline as well as strongly distorted areas with planar defects. The latter are probably due to sodium loss and disorder which is also detected by (23)Na solid state NMR. The (57)Fe-M?ssbauer spectrum of Na(1-y)Fe(2-x)As(2) shows one type of iron atoms in tetrahedral coordination. All results point to one crystallographic phase with very small domains due to fluctuations of the chemical composition. From electronic reasons we suggest the superconducting phase is presumably NaFe(2)As(2) in the ordered fractions of the sample.     

Accurate variational calculations of the ground 2Po(1s22s22p) and excited 2S(1s22s2p2) and 2Po(1s22s23p) states of singly ionized carbon atom

In this article we report accurate nonrelativistic variational calculations of the ground and two excited states of C(+) ion. We employ extended and well optimized basis sets of all-electron explicitly correlated Gaussians to represent the wave functions of the states. The optimization of the basis functions is performed with a procedure employing the analytic gradient of the energy with respect to the nonlinear parameters of the Gaussians. The calculations explicitly include the effects due to the finite nuclear mass. The calculated transition energies between the three states are compared to the experimentally derived values. Finally, we present expectation values of some small positive and negative powers of the interparticle distances and contact densities.     

Thermodynamics of carbon dioxide and carbonic acid: (a) the standard enthalpies of solution of Na2CO3(s), NaHCO3(s), and CO2(g) in water at 298.15 K; (b) the standard enthalpies of formation,standard Gibbs energies of formation,and standard entropies of CO2(aq), HCO3−(aq), CO32−(aq), NaHCO3(s), Na2CO3(s), Na2CO3·H2O(s), and Na2CO3·10H2O(s)

Enthalpies of solution of CO₂(g), NaHCO₃(s), and Na₂CO₃(s) in excess NaOH solution were measured at 298.15 K by solution calorimetry. The results were reduced to standard-state processes through use of results from a preceding paper, and standard enthalpies of solution for CO₂(g), NaHCO₃(s), and Na₂CO₃(s) in water at 298.15 K were found to be: ?(4720 ± 40), (4474 ± 30), and ?(6371 ± 30) cal_th mol^?1 respectively. The results of equilibrium studies involving CO₂(g) (solubility and e.m.f. studies) were reviewed and assembled,together with entropies for related solids. Standard values of ΔH_f^o, ΔG_f^o, and S^o at 298.15 K were evaluated for CO₂(aq, non-ionized), HCO₃^?(aq), CO₃^2?(aq), NaHCO₃(s), Na₂CO₃(s), Na₂CO₃·H₂O(s), and Na₂CO₃·10H₂O(s).     

Inner-valence photoionization of O((1)D): experimental evidence for the 2s(2)2p(4)((1)D)-->2s(1)2p(5)((1)P) transition

Photoionization and autoionization of electronically excited atomic oxygen O((1)D) are investigated in the energy range between 12 and 26 eV using tunable laser-produced plasma radiation in combination with time-of-flight mass spectrometry. A broad, asymmetric, and intense feature is observed that is peaking at 20.53+/-0.05 eV. It is assigned to the 2s(2)2p(4)((1)D)-->2s(1)2p(5)((1)P) transition, which subsequently autoionizes by a Coster-Kronig transition, as predicted by the previous theoretical work [K. L. Bell et al., J. Phys. B 22, 3197 (1989)]. Specifically, the energy of the unperturbed transition occurs at 20.35+/-0.07 eV. Its shape is described by a Fano profile revealing a q parameter of 4.25+/-0.8 and a width of gamma=2.2+/-0.15 eV. Absolute photoionization cross section sigma is derived, yielding sigma=22.5+/-2.3 Mb at the maximum of the resonance. In addition, weak contributions to the O((1)D) yield from dissociative ionization originating from molecular singlet oxygen [O(2)((1)Delta(g))] are identified as well. Possible applications of the 2s(2)2p(4)((1)D)-->2s(1)2p(5)((1)P) transition as a state-selective and sensitive probe of excited oxygen in combination with photoionization mass spectrometry are briefly discussed.     

四核钼亚硝基双硫配合物Na2[Mo4O(S2)6(NO)4].3H2O的合成和晶体结构

本文报道了四核钼亚硝基双硫配合物——Na_2[MO_4O(S_2)_6(NO)_4]·3H_2O的合成和晶体结构。该晶体属单斜晶系;空间群Ic;晶胞参数a=10.322(2),b=22.945(6),c=10.312(2)A,β=90.02(1)°;Z=4;D~c=2.731g·cm~(-3)。在CAD4四圆衍射仪上录谱,其中I≥3σ(I)的独立衍射点为2258个。晶体结构采用直接法解出,并用全矩阵最小二乘法修正,最终偏离因子R为0.053。研究结果表明,阴离子是以四配位氧为中心的四核钼硫配合物,氧原子处在四个钼组成的稍为扭曲的四面体中心。每对Mo原子均由S_2配位基端接或侧接桥联。Mo(IV)原子配位为扭曲的五角双锥,其中线性亚硝基NO基团及桥基氧原子处在五角双锥轴线上,五个硫原子在五角双锥赤道面上,阴离子构型接近S_4对称性。     

Poly(arylene ether)s,poly(arylene thioether)s,and poly(arylene sulfone)s derived from a dihydroxy(imidoarylene) monomer

Novel poly(arylene ether)s, poly(arylene thioether)s, and poly(arylene sulfone)s were synthesized from the dihydroxy(imidoarylene) monomer 1 . The syntheses of poly(arylene ether)s were carried out in DMAc in the presence of anhydrous K₂CO₃ by a nucleophilic substitution reaction between the bisphenol and activated difluoro compounds. Poly(arylene thioether)s were synthesized according to the recently discovered one-pot polymerization reaction between a bis(N,N′-dimethyl-S-carbamate) and activated difluoro compounds in the presence of a mixture of Cs₂CO₃ and CaCO₃. The bis(N,N′-dimethyl-S-carbamate) 3 was synthesized by the thermal rearrangement reaction of bis(N,N′-dimethylthiocarbamate) 2 , which was synthesized from 1 by a phase-transfer catalyzed reaction. The poly(arylene thioether)s were further oxidized to form poly(arylene sulfone)s, which would be very difficult, if not impossible, to synthesize by other methods. All of the polymers described have extremely high T_gs and thermal stability as determined from DSC and TGA analysis. Poly(arylene sulfone)s have the highest T_gs and they are in the range of 298–361°C. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1201–1208, 1998     

The role of an initial Na(3p) state alignment in 1 keV H++Na(3p)→H(2p)+Na+ collisions

Charge exchange in 1 keV H⁺+Na→H(2p)+Na⁺ is studied in a Lyman-α scattered particle coincidence experiment. An initial Na(3p) state is prepared by laser-optical pumping; its alignment is controlled by the laser light polarization. The results are compared to a 34 coupled-channels calculation (R. Shingal), and discussed on the basis of an asymptotic model of the charge exchange process.     

Study on the reversible electrode reaction of Na(1-x)Ni(0.5)Mn(0.5)O2 for a rechargeable sodium-ion battery

Layered NaNi(0.5)Mn(0.5)O(2) (space group: R ?3m), having an O3-type (α-NaFeO(2) type) structure according to the Delmas' notation, is prepared by a solid-state method. The electrochemical reactivity of NaNi(0.5)Mn(0.5)O(2) is examined in an aprotic sodium cell at room temperature. The NaNi(0.5)Mn(0.5)O(2) electrodes can deliver ca. 105-125 mAh g(-1) at rates of 240-4.8 mA g(-1) in the voltage range of 2.2-3.8 V and show 75% of the initial reversible capacity after 50 charge/discharge cycling tests. In the voltage range of 2.2-4.5 V, a higher reversible capacity of 185 mAh g(-1) is achieved; however, its reversibility is insufficient because of the significant expansion of interslab space by charging to 4.5 V versus sodium. The reversbility is improved by adding fluoroethylene carbonate into the electrolyte solution. The structural transition mechanism of Na(1-x)Ni(0.5)Mn(0.5)O(2) is also examined by an ex situ X-ray diffraction method combined with X-ray absorption spectroscopy (XAS). The staking sequence of the [Ni(0.5)Mn(0.5)]O(2) slabs changes progressively as sodium ions are extracted from the crystal lattice. It is observed that the original O3 phase transforms into the O'3, P3, P'3, and P3" phases during sodium extraction. XAS measurement proves that NaNi(0.5)Mn(0.5)O(2) consists of divalent nickel and tetravalent manganese ions. As sodium ions are extracted from the oxide to form Na(1-x)Ni(0.5)Mn(0.5)O(2), nickel ions are oxidized to the trivalent state, while the manganese ions are electrochemically inactive as the tetravalent state.     

Time(s)

正Fig. 5. (a) TPV signal of Ti‐Fe2O3/25Cd S sample with FTO substrate side under 405‐nm laser irradiation and FTO electrode side under 532‐nm laser illumination; (b) TPV signal of Ti‐Fe2O3/25Cd S sample with FTO electrode side under 405‐nm laser illumination and FTO substrate side under532‐nm laser illumination.     

Na10(Na,Mn)7Mn43(PO4)36: a new synthetic fillowite‐type phosphate

Na₁₀(Na,Mn)₇Mn₄₃(PO₄)₃₆ (sodium manganese phosphate) was synthesized hydrothermally at 873 K and 0.35 GPa. The complex crystal structure is almost identical to that of natural fillowite‐type phosphates and can be described as a hexagonal packing of three types of rods parallel to the c axis. The rods are constituted by an alternation of five‐ to seven‐coordinated Mn sites [average Mn—O = 2.243 (3) Å], of six‐ to nine‐coordinated Na sites [average Na—O = 2.590 (3) Å], of PO₄ tetrahedra [average P—O = 1.548 (3) Å] and of cation vacancies.