High-Resolution Infrared and Millimeter-Wave Study of the v(3) = 1 State of HSiF(3) and DSiF(3)

Millimeter-wave spectra of HSiF₃ and DSiF₃ in the v₃ = 1 excited state have been measured from 100 to 490 GHz. Infrared spectra have been recorded in the ν₃ regions, ν₀ 424.0301 and 420.9320 cm⁻¹ in HSiF₃ and DSiF₃, respectively, with a resolution of 2.4 × 10⁻³ cm⁻¹. Since in both species the parameters α^B₃ and α^C₃ have very similar values, no K structure could be resolved in the ^QP and ^QR clusters for low-to-medium K values. For high J the effect of the ground state D_JK term more and more dominates and spreads the J clusters into opposite directions such that medium-to-high K components, particularly those with K = 3p, are resolved. Rotational and infrared data have been fitted together using a model up to sextic centrifugal distortion constants. No perturbations were indicated. Hot bands (ν₃ + nν₆)–nν₆ with n = 1, 2, and 3 have been detected and analyzed.     

Doppler-limited spectroscopy of the 3ν3 band of SF6

The strongest portion of the 3ν₃ band of SF₆ has been recorded at T = 160 and 295 K with Doppler-limited resolution using a tunable laser difference-frequency spectrometer. The structure in this band has been identified with the P, Q, and R branches of one F_1u sublevel (with essentially l = 1 character) within the 3ν₃ vibrational manifold. Preliminary effective rotational constants have been obtained for this band from which the anharmonic parameters X₃₃, G₃₃, and T₃₃ can be estimated. The role of hot bands and of the other anharmonic sublevels is discussed in relation to prior interpretations of low resolution spectra and of the initial isotope selective stages of CO₂ laser photo-dissociation of SF₆.     

Prediction of the inversion splittings of the nv 2 vibrational levels in phosphine (PH3, PD3 and PMu3)

Inversion splittings of the nv ₂ vibrational levels in PH₃ and PD₃ have been calculated using a theoretical model developed by us for molecular inversion in XY₃ pyramidal molecules and the slightly modified results of an ab initio SCF-LCAO-MO calculation of the double minimum potential function for PH₃ by Lehn and Munsch. Inversion splittings have been predicted also for the chemical compound PMu₃, where Mu is muonium.     

石墨/Li（Ni1/3Co1/3Mn1/3）O2电池充放电过程中电极材料的XRD研究

利用XRD系统地研究了石墨/Li（Ni_1/3Co_1/3Mn_1/3）O₂ 18650型锂离子电池充放电过程中正负极活性材料的晶体结构和微结构的变化.已观测到,由于Li原子的脱嵌,使得LiMO₂点阵参数a缩小,c增大,微应变增大,衍射强度比I₁₀₄/I₁₀₁和I₀₁₂/I₁₀₁降低;此外,由于Li原子的嵌入,2H-石墨的点阵参数a和c,以及微应变ε和堆垛无序度P都增加.同时,讨论了活性材料Li（Ni_1/3Co_1/3Mn_1/3）O₂和石墨在电池充放电过程中的嵌脱锂的物理机理.在充电时,正极Li（Ni_1/3Co_1/3Mn_1/3）O₂中处于（000）位的Li原子优先脱离晶体点阵,继后才是位于（2/3 1/3 1/3）和（1/3 2/3 2/3）位的Li原子离开点阵.锂嵌入石墨,优先进入碳原子六方网格面间的间隙位置,当负极的堆垛无序度达到一定值后,3R相逐渐析出.当电池满充或过充时,在六方石墨中形成LiC₁₂和LiC₆相.放电时,与上述过程相反,但并非是完全可逆的. 关键词： 锂离子电池 微结构 X射线衍射 嵌脱锂物理机理     

Effect of Hydrostatic Pressure on the Dielectric Response of Pb(Mg1/3Nb2/3)O3 Relaxor

The effect of hydrostatic pressure on the dielectric response of Pb(Mg_1/3Nb_2/3)O₃ relaxor single crystal was studied. An increase in the dispersion of the dielectric anomaly, characteristic of the relaxors, was observed: pressure-induced downward shift of the temperature T _m of permittivity maximum at 1 kHz amounts to dT _m /dp = ? 3.8 K/100 MPa, whereas that measured at 1 MHz equals ? 3.3 K/100 MPa. Analysis of the dielectric response of the highly polarizable Pb(Mg_1/3Nb_2/3)O₃ shows that hydrostatic pressure results in a decrease of the correlation radius r _c of polar nanodomains, as well as their activation energy.     

Mechanism and nature of phase transitions in the (NH4)3MoO3F3 oxyfluoride

The temperature dependences of the heat capacity, the unit cell parameter, and the permittivity for the (NH₄)₃MoO₃F₃ cryolite (space group Fm $ \overline 3 The temperature dependences of the heat capacity, the unit cell parameter, and the permittivity for the (NH₄)₃MoO₃F₃ cryolite (space group Fm m) are investigated. It is revealed that the compound undergoes ferroelectric and ferroelastic structural phase transitions at temperatures of 297 and 205 K, respectively. The mechanism of structural distortions is discussed in terms of the entropy parameters, pressure-temperature phase diagrams, and electron density maps for critical atoms. An analysis is made of the influence of the cation size and shape on the phase transitions in oxyfluorides of the general formula A ₂ A′MO₃ (A,A′ = NH₄, K; M = Mo, W). Original Russian Text ? I.N. Flerov, V.D. Fokina, A.F. Bovina, E.V. Bogdanov, M.S. Molokeev, A.G. Kocharova, E.I. Pogorel’tsev, N.M. Laptash, 2008, published in Fizika Tverdogo Tela, 2008, Vol. 50, No. 3, pp. 497–506.     

High-Resolution Infrared Spectra of the ν2, ν3, ν4, and 2ν3 Bands of SO3

New measurements are reported for the infrared spectrum of sulfur trioxide, ³²S¹⁶O₃, with resolutions ranging from 0.0015 cm⁻¹ to 0.0025 cm⁻¹. Rovibrational constants have been measured for the fundamentals ν₂, ν₃, and ν₄ and the overtone band 2ν₃. Comparisons are made with the earlier high-resolution measurements on SO₃, and the high correlation among some of the constants related to the Coriolis coupling of the ν₂ and ν₄ levels is discussed in order to understand the areas of disagreement with the earlier work. Splittings of some of the levels are observed and the splitting constant for K=3 of the ground state is determined for the first time. Other observed splittings include the K=1 levels of 2ν₃ (l=2), the K=2 levels of ν₃ and ν₄, and the K=3 levels of ν₂. The analysis shows that there are level crossings between the l=0 and l=2 states of 2ν₃ that allow one to determine the separation of the subband centers for these two states even though access to the l=0 state from the ground state is electric-dipole forbidden. This is a generalized phenomenon that should be found for many other molecules with the same symmetry. The l-type resonance constant, q₃, that causes the splitting of the l₃=±1, k=±1 levels of ν₃ also couples the l₃=0 and 2 states of 2ν₃.     

BiFeO_3结构性质与相转变的第一性原理研究

采用基于密度泛函理论的第一性原理计算,系统地研究了BiFeO3的7种不同空间群(R3c,R3m,P4mm,Cm,Pm3m,R3m和R3c)结构及其转变关系.结果表明,铁电相R3c结构是基态,不同结构之间也存在着一定的转变关系,其变化主要包括两种形式,在[111]方向上Bi3+相对FeO6八面体存在一定的位移和FeO6八面体绕[111]极化轴的反铁扭曲旋转.此外,还得出BiFeO3的薄膜结构受到衬底结构的作用会导致其从三方相(R3c)向四方相(P4mm)转变.     

Thermal conductivity of the spin-Peierls compound CuGeO3

The thermal conductivity of the pure and zinc-doped spin-Peierls compound CuGeO₃ is investigated for the first time. Characteristic features reflecting the changes in the phonon spectrum of the crystals are observed in the k(T) curves at a transition into the dimerized state in CuGeO₃ at T _sp =14.2 K and in Cu_0.98Zn_0.02GeO₃ at T _sp =10.6 K. Near the spin-Peierls transition temperature T _sp the thermal conductivity of Cu_0.98Zn_0.02GeO₃ (k=3 W/m·K) is much less than the thermal conductivity of CuGeO₃ (k=21.5 W/m·K). Pis’ma Zh. éksp. Teor. Fiz. 66, No. 12, 823–826 (25 December 1997)     

Layer structures BaO-BaTiO3 in the region of p-type conductivity on the surface of BaTiO3

X-ray diffraction measurements on the surface of polycrystalline BaTiO₃ show that a reversible process of defect segregation occurs in the temperature range from 500 to 1000° C and in the air pressure range from 10^–2 to 760 torr. This causes the appearance and disappearance of new crystalline phases of the formula Ba _n+1Ti _n O_3n+1 (n=1,2,3). These findings amend the present defect models developed on the basis of measurements of the p-type equilibrium conductivity as a function of oxygen partial pressure.     

Application of the Keating Bendings to ALCL3 and SO3: Preliminary Communication

Force fields from literature for the degenerate (E') vibrations of AlCl₃ and SO₃ are transferred from the valence symmetry coordinates to the central- and Keating symmetry coordinates. In both cases it is found |F ₁₂ ^k| > |F ₁₂| > |F ₁₂ ^c|.     

Ionic conductivity of isostructural crystals of the superionic conductors Li3Fe2(PO4)4 and Li3Sc2(PO4)3

The results of measurements of the ionic conductivity σ in Li₃M₂(PO₄)₃ (M=Fe, Sc) single crystals along various crystallographic directions are analyzed. Possible causes of the different behavior of σ in the isostructural crystals are discussed: a jump of the conductivity in the transition to the superionic phase in Li₃Sc₂(PO₄)₃ and its absence in Li₃Fe₂(PO₄)₃; the existence of a conductivity maximum in different crystallographic directions (along the c axis in Li₃Sc₂(PO₄)₃ and along the a axis in Li₃Fe₂(PO₄)₃). Fiz. Tverd. Tela (St. Petersburg) 39, 83–86 (January 1997)     

Piezoelectric properties of PbHfO3–PbTiO3–Pb(Mg1/3Nb2/3)O3 ternary ceramics

(1 – x)Pb(Hf_1–yTi_y)O₃–x Pb(Mg_1/3Nb_2/3)O₃ (x = 0.1 ～ 0.25, y = 0.555) ternary piezoelectric ceramics were prepared using the two‐step precursor method. Morphotropic phase boundary (MPB) compositions, located at x = 0.18 ～ 0.22, were confirmed using X‐ray diffraction and by their dielectric, piezoelectric and ferroelectric properties. The optimum dielectric and piezoelectric properties were achieved for the MPB composition 0.8Pb(Hf_0.445Ti_0.555)O₃–0.2Pb(Mg_1/3Nb_2/3)O₃, with dielectric permittivity ε_r, piezoelectric coefficient d₃₃, planar electromechanical coupling k_p and Curie temperature T_C being on the order of 2800, 680 pC/N, 70% and 276 °C, respectively. Of particular significance is that the new ternary ceramics exhibit comparable piezoelectric and electromechanical properties to commercial PZT5H ceramics, but with much improved T_C, showing a potential for applications at elevated temperature. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Observation of the ν3 Raman band of S3− inserted into sodalite cages

The S₃⁻ radical anion is observed in several systems: non‐aqueous polysulfides solutions, doped alkali halides, ultramarine pigments (UP) for which S₃⁻ is the blue chromophore and S₂⁻ is the yellow one and pigments of zeolite 4A structure. The S₃⁻ ion has C_2V symmetry, and therefore its three vibrational modes should be observed in the Raman and in IR spectra. In resonance Raman spectroscopy, only the symmetric stretching mode ν₁ and the bending mode ν₂ have been observed, whereas the anti‐symmetric stretching mode ν₃ has never been observed whatever the system. In this work, we confirm that ν₃ is not observed in solutions with resonance Raman spectroscopy. However, our investigation of several blue UP, with various concentrations of S₂⁻, shows that there is a superposition of two bands at ca 590 cm⁻¹: the first is assigned to ν (S₂⁻) and the second to ν₃ (S₃⁻). With the 457.9 nm excitation line, for which the resonance conditions are simultaneously fulfilled for S₂⁻ and S₃⁻, the band at ca 590 cm⁻¹ is the sum of the contributions of both ν (S₂⁻) and ν₃ (S₃⁻) vibrations, while, with the 647.1 nm line, which only satisfies the resonance conditions of S₃⁻, the band at ca 584 cm⁻¹ must be assigned only to ν₃ (S₃⁻). Furthermore, ν₃ (S₃⁻) is observed in green UP and in pigments of zeolite structure. The ν₃ vibration of S₃⁻, which is observed neither in polysulfide solutions nor in doped alkali halides in resonance Raman conditions, can therefore be observed when this species is inserted into the β‐cages of the sodalite or of the zeolite 4A structures. So, the band at ca 590 cm⁻¹ cannot always be assigned to S₂⁻ in these systems. This implies that the concentration of S₂⁻ in UP must be reconsidered. Copyright © 2007 John Wiley & Sons, Ltd.     

Analysis of the Coriolis-coupled band system of ν5, ν2, and 2ν3 of methyl-d3 iodide

The Coriolis-coupled band system of ν₅, ν₂, and 2ν₃ of CD₃I was analyzed by making use of all of the experimental data now available. These data included the high-resolution infrared spectra, microwave spectra, and laser Stark spectra. The analysis gave values, more precise than before, of the spectroscopic constants for ν₅, ν₂, and 2ν₃ and the interaction constants. The determination of the rotational constant A for 2ν₃ gave a value for , with which all of the α^A constants for CD₃I have been completed. These α^A values were incorporated with the known value of A₆ to give a value for A₀.     

Comparison between the magnetic specific heat of NdBa2Cu3O x and DyBa2Cu3O x

Low temperature heat-capacity measurements have been performed to study the magnetic ordering in NdBa₂Cu₃O _x and DyBa₂Cu₃O _x . In order to investigate the type of ordering, magnetic fields up to 6 T and hydrostatic pressures up to 4.5 kbar were applied. While for NdBa₂Cu₃O _x and DyBa₂Cu₃O _x both the fully oxidized and the fully oxygen reduced samples display long rang antiferromagnetic ordering, only magnetic short range interaction could be found for samples in an intermediate range of oxygen concentration. For NdBa₂Cu₃O _x , where superexchange is believed to be the dominant magnetic interaction,T _N is three times higher in the sample withx=6.26 compared to the one withx=6.98. In contrast,T _N of DyBa₂Cu₃O _x is almost oxygen independent as expected for this mainly dipolar interacting system.     

Room temperature emission from the Pr3+ 1 S 0-level in PrF3

PrF₃ as well as PrF₃-LiF and PrF₃-MgF₂ mixtures were investigated by means of high-energetic excitation with synchrotron radiation. In the PrF₃ emission spectrum bands due to the intra-configurational 4f²4f² transitions originating from the ¹S₀ level of the Pr³⁺ ion have been identified. The emission from the ³P₀ multiplet is very weak due to non-radiative decay by cross-relaxation processes. Therefore, PrF₃ is not an efficient direct cascade emitter. In the PrF₃ excitation spectra in the ultraviolet/vacuum-ultraviolet spectral range, the ³H₄¹S₀ transition at 46858 cm^-1 as well as broad bands due to the inter-configurational 4f²4f5d transitions are observed. By comparison with data of Pr³⁺ doped YF₃, the branching ratios of the emission transitions for PrF₃ from the ¹S₀ were determined; these are 0.008, 0.075, 0.262, 0.023 and 0.629 for transitions ¹S₀³H₄, ³F₄, ¹G₄, ¹D₂ and ¹I₆, respectively. For the polycrystalline PrF₃-LiF and PrF₃-MgF₂ samples investigated by us, the measured emission and excitation spectra are nearly identical to those of PrF₃. For polycrystalline PrF₃-KMgF₃ the observed spectra are superpositions of the PrF₃ and Pr³⁺:KMgF₃ spectra. PACS 42.70.-a; 78.55.-m; 78.55.Hx     

Al2O3Hx(x=1—3)分子团簇的结构与光谱研究

用密度泛函理论(DFT)的B3lyp方法在6-311++g(d,p)水平上对Al₂O₃H_x(x=1—3)分子的几何构型, 电子结构, 振动频率等性质进行了系统研究. 并给出了它们可能基态结构的总能量(E_T), 零点能(E_z), 摩尔热容(C_v), 标准熵(S), 原子化能(ΔE_m), 垂直电离能(IP)及垂直电子亲和能(E_A). Al₂O₃H和Al₂O₃H₂分子可能的基态的几何构型都为平面结构. Al₂O₃H₃的两个可能为基态的几何构型都是在立体Al₂O₃(D_3h)的几何结构基础上加三个氢原子构成. 这三个分子的能量最低结构为Al₂O₃H(²A′)C_s, Al₂O₃H₂(¹A′) C_s, Al₂O₃H₃ (²A) C₁.     

Charge compensation and the luminescence of Cr3+ in KMgF3

Studies of the photoluminescence spectra of Cr³⁺ ions in KMgF₃ crystals co-doped with Cr³⁺ and Ni²⁺ ions are reported. Several crystal field sites are identified by the different R-line spectra due to the ² E⁴ A ₂ transition and broadband luminescences associated with the ⁴ T ₂⁴ A ₂ transitions. Cr³⁺ ions substituting without local charge compensation on the octahedral Mg²⁺ site give rise to a low temperature R line in photoluminescence at =702.3 nm with a radiative decaytime of 3 ms at T=14 K. At T=300 K this isotropic centre gives rise to an unpolarized broadband ⁴ T ₂⁴ A ₂ emission, which results from the thermal occupancy of an excited ⁴ T ₂ state just above the ² E level which, at lower temperature, gives rise to emission in the R-line. Other crystal field sites are due to some Cr³⁺ ions having Mg²⁺ or K⁺ vacancies in nearest-neighbour positions, these vacancies being required to maintain charge neutrality in doped fluoride perovskites. The Cr³⁺–K⁺ vacancy complex results in the centre having trigonal symmetry, and low temperature, photoluminescence via R ₁ and R ₂ lines at 716.8 nm and 716.0 nm, respectively. Finally, Cr³⁺ ions having a nearest neighbour Mg²⁺ vacancy have tetragonal symmetry, experiencing weak crystal fields. In consequence, the ⁴ T ₂ level lies below ² E and the photoluminescence spectrum at low temperature takes the form of a polarized broad ⁴ T ₂⁴ A ₂ band with peak at 760 nm and radiative decaytime of 54 s.     

Fine structure and isotope shift of the 3s4d 3 D-3s3p 3 P, 3s5d 3 D-3s3p 3 P and 3p 2 3 P-3s3p 3 P Transitions of MgI

Summary We report the measurements of the³ D(3s4d)-³ P(3s3p)³ D(3s5d)-³ P(3s3p), and³ P(3p ²)-³ P(3s3p) transition frequency of MgI, the fine-structure separation and isotope shift between²⁴Mg and²⁶Mg. The measurements have been performed in a metastable atomic beam; a good agreement is found for data already existing in the literature. The accuracy of the measurements reported in this paper is mainly limited by the Doppler broadening of theI ₂ transitions used as a reference and by the precision in the knowledge of the related wavelengths.