Electrochemical behavior of nanostructured LiV3O8 in aqueous LiNO3 solution

Despite the large number of studies on the electrochemical behavior of LiV₃O₈ as a cathode material in nonaqueous lithium ion batteries, little information is available about the electrochemical behavior of LiV₃O₈ as an anode material in aqueous rechargeable lithium batteries. In this work, nanostructured LiV₃O₈ is successfully prepared using a low-temperature solid-state method. The electrochemical properties of the LiV₃O₈ electrode in 1 M, 5 M, and saturated LiNO₃ aqueous electrolytes have been characterized by cyclic voltammetry, electrochemical impedance spectroscopy, and galvanostatic charge/discharge experiments. The results show that LiV₃O₈ electrode in saturated LiNO₃ electrolyte exhibits good electrochemical performance in terms of specific capacity and electrochemical cycling performance. LiV₃O₈ electrode can be reversibly cycled in saturated LiNO₃ aqueous electrolyte for 300 cycles at a rate of 0.5 C (300 mA g⁻¹ is assumed to be 1 C rate) with impressive specific capacities.     

La0.67Ca0.33MnO3薄膜皮秒光电效应

在1064 nm波长脉冲激光（脉宽25 ps）的照射下，钙钛矿氧化物薄膜La0.67Ca0.33MnO3/SrTiO3具有超快光电效应，对激光脉冲显示ps量级的响应时间，上升沿响应时间300 ps，半高宽700 ps，同时，对激光能量的响应灵敏度为500 mV/mJ。     

Zero field splittings of Gd3+IN Nd2(SO4)3 · 8H2O and Sm2(SO4)3 · 8H2O crystals at 273 K

The electron paramagnetic resonance (EPR) of Nd₂(SO₄)₃ · 8H₂O and Sm₂(SO₄)₃ · 8H₂O doped with Gd³⁺ has been carried out at 273 K and the spin-Hamiltonian parameters are deduced. The zero field splittings have been computed and compared with those observed directly by Bogle and Symmons. It is found that the discrepancy in the zero field splittings. between computed and directly observed values falls within the range of linewidths of directly observed values.     

Lithium insertion into Li4V3O8

The lithium insertion characteristics of lithium vanadate, Li₄V₃O₈, were investigated using LiV₃O₈ prepared by the precipitation technique as the starting material. The Li₄V₃O₈ phase was formed by lithiation over x=1.5 in Li_1+xV₃O₈, and the diffusion of lithium in this phase determined the reaction rate of insertion more than x=1.5. Improvement of insertion kinetics in the Li₄V₃O₈ phase extended the lithium insertion limit from x=3.2 to x=4.0, compared with the case of LiV₃O₈ by conventional high temperature synthesis. Lithium insertion proceeds as the single-phase reaction in the range of 3.2<x<4.0.     

The ν3 and 2ν3 bands of SO3, SO3, SO3, and SO3

This sixth of a series of publications on the high-resolution rotation-vibration spectra of sulfur trioxide reports the results of a systematic study of the ν₃ and 2ν₃ infrared bands of the four symmetric top isotopomers ³²S¹⁶O₃, ³²S¹⁸O₃, ³⁴S¹⁶O₃, and ³⁴S¹⁸O₃. An internal coupling between the l=0(A₁^′) and l=2(E^′) levels of the 2ν₃ states was observed. This small perturbation results in a level crossing between |k−l|=9 and 12, in consequence of which the band origins of the A₁^′,l=0 “ghost” states could be determined to a high degree of accuracy. Ground and upper state rotational constants as well as vibrational anharmonicity constants are reported. The constants for the center-of-mass substituted species ³²S¹⁶O₃ and ³⁴S¹⁶O₃ vary only slightly, as do the constants for the ³²S¹⁸O₃, ³⁴S¹⁸O₃ pair. The S-O bond lengths for the vibrational ground states of the species ³²S¹⁶O₃, ³⁴S¹⁶O₃, ³²S¹⁸O₃, and ³⁴S¹⁸O₃ are, respectively, 141.981 99(1), 141.979 38(6), 141.972 78(8), and 141.969 93(8) pm, where the uncertainties, given in parentheses, are two standard deviations and refer to the last digits of the associated quantity.     

新型钙钛矿铜氧材料Sr8 CaRe3 Cu4 O24的亚铁磁和轨道有序性质

用密度泛函理论和格林函数方法研究了新型钙钛矿铜氧材料Sr8CaRe3Cu44O24的电子结构和磁性性质.所得结果与实验符合得很好,表明这种材料是绝缘体,每个元胞有1.0μB的磁矩.磁矩主要在Cu原子上,相邻Cu原子上的磁矩反平行排列.非磁的Re原子使得Cu上的d轨道有序排列,这导致这种材料有很高的居里温度(TC≈440K).基于密度泛函的结果,用海森伯模型描述了材料的电子自旋自由度,并用格林函数方法研究了材料有限温度下的磁性行为,所得结果和实验一致,表明自旋为1和自旋为1/2磁矩交错排列的海森伯模型可很好地描述这种材料的磁性性质.     

Temperature dependence of ESR anisotropy in La7/8Sr1/8MnO3

We report X-ray diffraction, DC-susceptibility, electron spin resonance (ESR), and dilatometry measurements carried out on an La_7/8Sr_1/8MnO₃ single crystal. Thermal expansion was measured along different crystallographic axes using a three-terminal dilatometer. The sharp anomalies observed in the temperature dependence of Δl/l allowed us to locate the Jahn–Teller transition at T_JT=285(1) K. ESR experiments were carried out in the paramagnetic regime from 220 to 570 K, at 9.4 GHz. We measured the ESR line width ΔH_pp(T) with the magnetic field parallel to the crystallographic directions [1 0 0] and [0 0 1], referred to the orthorhombic (Pbnm) axes. We correlate the temperature dependence of ΔH_pp with the structural changes of the lattice.     

Photophysical analysis of the organic complex [Eu(C12H8N2)2](NO3)3

We have determined the photophysical properties of [Eu(C₁₂H₈N₂)₂](NO₃)₃, (EuPhen), a complex which is very promising for photonic and optoelectronic applications, because of its easy synthetic procedure and high thermal stability (up to 300 °C) combined with large sensitization efficiency and good emission quantum yield. Available experimental absorption and emission data have been analyzed by using Judd-Ofelt analysis. Moreover, semi-empirical calculations have been used to determine the structure of the complex and to interpret the convoluted shape of the absorption spectrum.     

Magnetic and structural studies of Cr2O5 and Cr3O8

The infrared spectra, indexed X-ray powder diffraction patterns, magnetic susceptibilities between 80 and 300 K, and electron paramagnetic resonance spectra at 80 and 300 K are reported for Cr₂O₅ and Cr₃O₈. The results indicate that both oxides are Cr³⁺/Cr⁶⁺ mixed-valence compounds which contain CrO₆ octahedra and CrO₄ tetrahedra in different ratios. The valence formula for Cr₂O₅ is Cr³⁺₂Cr⁶⁺₄O₁₅ and that of Cr₃O₈ is Cr³⁺₂Cr⁶⁺₇O₂₄. The X-ray powder data for Cr₂O₅ and Cr₃O₈ could be indexed on the basis of a monoclinic unit cell $\text{(a = 12.01(2), b = 8.52(1), c = 9.39(1)}\text{A}\text{?}\text{β = 92.0(1)°)}$ and an orthorhombic unit cell $\text{(a = 12.01(7), b = 36.60(7) and c = 3.82(1)}\text{A}\text{?}\text{)}$, respectively.     

Incommensurate modulations in Ba2TiSi2O8, Sr2TiSi2O8, and Ba2TiGe2O8

Incommensurate modulations in Ba₂TiSi₂O₈, Sr₂TiSi₂O₈, and Ba₂TiGe₂O₈ are compared based on their corresponding electron diffraction patterns. The dependence of the modulations on chemical composition provides a suitable model system for the investigation of incommensurations in framework structures using high-resolution transmission electron microscopy (HRTEM). A widening of quantitative HRTEM utilising the concept of rigid units is proposed allowing for a determination of atomistic displacements responsible for the formation of incommensurately modulated structures.     

Dense-Kondo antiferromagnetism in (CePd3)8Ge

We report the existence of (CePd₃)₈Ge and (LaPd₃)₈Ge, and find them to have the same cubic superstructure as reported for (CePd₃)₈T (T=Ga, In, Sn, Sb, Pb and Bi) by Gordon and co-workers [1 and 2]. The cerium ions in (CePd₃)₈Ge are trivalent and undergo an antiferromagnetic transition below 5 K with a dense-Kondo-lattice behaviour.     

Optical conductivity of CePd3, YPd3 and PrPd3

The optical conductivity of intermediate valence CePd₃ at 300 K exhibits a maximum near 16 meV, which is absent in the reference materials YPd₃ and PrPd₃. Using a modified Drude model with a memory function ansatz this anomaly has been identified as a resonant electron-electron scattering process of conduction electrons at the localized 4f states near the Fermi level E_F. The model fit gives estimates of the width of the 4f states, of their separation from E_F and of the f-d hybridization energy. Intra-4f transitions of CePd₃ are stronger compared to those of PrPd₃ due to the stronger f-d hybirdization. 4d→4f transition energies of CePd₃ are reduced due to an electron-hole Coulomb binding energy.     

The first-principles study of ferroelectric behaviours of PbTiO3/SrTiO3 and BaTiOn/SrTiO3 superlattices

We have performed the first-principles calculation to investigate the origins of ferroelectricities and different po- larization behaviours of superlattices BaTiO3/SrTiO3 and PbTiO3/SrTiO3. The density of state （DOS） and electronic charge profiles show that there are strong hybridizations between atoms Ti and O and between atoms Pb and O which play very important roles in producing the ferroelectricities of superlattices BaTiO3/SrTiO3 and PbTiO3/SrTiO3. Ow- ing to the decline of internal electric field in SrTiO3 （ST） layer, the tetragonality and polarizations of superlattices decrease with increasing the fraction of SrTiO3 in the superlattices. We find that the polarization of PbTiO3/SrTiO3 is largerthan that of BaTiO3/SrTiO3 at the same ratio of components, because the polarization mismatch between PbTiO3 and SrTiO3 is larger than that between BaTiO3 and SrTiO3. The polarization and tetragonality are en- hanced with respect to those of bulk tetragonal BaTiO3 in the superlattices BaTiO3/SrTiO3, while the polarization and tetragonality are reduced with respect to those of bulk tetragonal PbTiO3 in superlattices PbTiO3/SrTiO3.     

EPR studies of Gd3+-doped Ce2(SO4)3.8H2O and La2(SO4)3.9H2O single crystals

EPR spectra of Gd³⁺-doped Ce₂(SO₄)₃.8H₂O and La₂(SO₄)₃.9H₂O single crystals have been measured with an X-band spectrometer at room and low temperatures. The absolute signs of spin Hamiltonian parameters have been determined for the La₂(SO₄)₃.9H₂O host from intensities of lines at liquid helium temperature; for the Ce₂(SO₄).8H₂O host the lines broaden considerably below 60 K, not permitting the determination of absolute signs of spin Hamiltonian parameters. The data are analysed using a rigourous least-squares procedure, fitting simultaneously all lines obtained for several orientations of the external magnetic field. The zero-field splittings have been computed for both the hosts. The characteristics of EPR spectra of Gd³⁺ in these hosts are compared with those obtained in other rare-earth trisulphate octahydrate hosts.     

Thermal stability of cubane C8H8

The reasons for the anomalously high thermal stability of cubane C₈H₈ and the mechanisms of its decomposition are studied by numerically simulating the dynamics of this metastable cluster at T = 1050–2000 K using a tight-binding potential. The decomposition activation energy is found from the temperature dependence of the cubane lifetime obtained from the numerical experiment; this energy is fairly high, E _a = 1.9 ± 0.1 eV. The decomposition products are, as a rule, either C₆H₆ and C₂H₂ molecules or the isomer C₈H₈ with a lower energy. Original Russian Text ? M.M. Maslov, D.A. Lobanov, A.I. Podlivaev, L.A. Openov, 2009, published in Fizika Tverdogo Tela, 2009, Vol. 51, No. 3, pp. 609–612.     

Li2K(IO3)3与Li2NH4(IO3)3的晶体结构

本文用X射线粉末法测定了Li₂K(IO₃)₃与Li₂NH₄(IO₃)₃的晶体结构和原子参数。发现Li₃K(IO₃)₃,Li₂NH₄(IO₃)₃与Li₂Rb(IO₃)₃同晶型,属单斜晶系,空间群为P2₁/α,每个单胞含有四个化合式量。室温的点阵常数分别为α=11.198?,b=11.046?,c=8.254?,β=111.53°,及α=11.327?,b=11.078?,c=8.341?,β=111.87°。讨论了二元化合物的形成与离子半径的关系。 关键词：     

Superconductivity of the graphite intercalation compounds KHgC8 and RbHgC8

Superconductivity was observed in the graphite intercalation compounds, KHgC₈ and RbHgC₈, using an AC induction technique. The transition temperatures were 1.90K and 1.44K for KHgC₈ and RbHgC₈ respectively. A full Meissner effect was observed for KHgC₈ with a temperature dependant anisotropy in critical field with a value of 25 ± 5 at T_c.     

Low temperature far IR spectra of (CH34)N NiCl3, (CH3)4N NiBr3 and (CD3)4N NiBr3

The known phase transition in (CH₃)₄N NiCl₃, at 171 K, has been characterised by far IR spectroscopy. The transition is explained as due to a formation of weak labile C-H,…, Cl hydrogen bonds at low temperatures, restricting the “free” internal rotations of the methyl groups and perhaps at the same time ordering the orientations of the tetramethylammonium ions. No similar transition in (CH₃)₄N NiBr₃ was found.