Surface segregation during the uptake of NO3 on coatings composed of NaI · 2H2O/NaBr · 2H2O and MgBr2 · 6H2O/MgCl2 · 6H2O binary salts: Solubility or deliquescence?

The uptake of NO₃ radicals on the surface of coatings prepared from the individual salts of NaI and NaBr dehydrates, hexahydrates of MgBr₂, and MgCl₂ and NaI · 2H₂O/NaBr · 2H₂O and MgBr₂ · 6H₂O/MgCl₂ · 6H₂O binary salts at various mole fractions of the doping salts, NaI · 2H₂O and MgBr₂ · 6H₂O in the initial aqueous solution was measured in a flow reactor by kinetic mass spectrometry. The dependences of the rates of the consumption of the reactant and of the formation of the products on the mole fraction of the doping salt made it possible to determine a quantitative relationship between the surface density of the doping salt and its mole fraction in the initial solution. A joint analysis of these dependences and the previously obtained data led to the conclusion that the deliquescence of the studied individual salts produces the predominant effect on the ratio between their surface densities.     

超分子化合物C11H6N2O·H3PO4·H2O的合成与晶体结构

采用水热反应法合成超分子化合物C11H6N2O·H3PO4·H2O,通过元素分析、红外光谱和X射线单晶衍射对其组成、结构进行分析.该化合物属于三斜晶系,空间群P-1,晶胞参数a=0.73350(6)nm,b=0.74191(7)nm,c=1.15692(14)nm,α=96.395(2)°,β=92.9940(10)°,γ=90.3440(10)°,V=0.62477(11)nm3,Z=2,F(000)=308,Dc=1.585g·cm-3,最终偏差因子R1=0.0521,wR2=0.1282.该化合物的不对称单元由3个独立的分子4,5-二氮芴-9-酮、磷酸和水分子构成,氢键连接分子形成三维超分子化合物.     

Spin-spin interaction of Ni2+ ions in ZnSiF6·6H2O

The angular dependences of the electron spin resonance spectrum of 1% Ni²⁺ ions in a ZnSiF₆·6H₂O matrix are investigated experimentally at 36 GHz and 4.2 K. Besides the main spectrum of the isolated ion, we observed a spectrum due to interacting pairs of Ni²⁺ ions, located in the first (nn) and second (2n) coordination spheres and coupled by, besides the magnetic dipole-dipole interaction, isotropic exchange: J _nn = (−197±1)×10⁻⁴, J _2nα = (−5±1)×10⁻⁴, and J _2nβ = (3±2)×10⁻⁴ cm⁻¹. Lines due to other isolated Ni²⁺ ions, which have a different initial splitting D, are also present in the spectrum with intensity comparable to the pair spectrum. Low-symmetry distortions of the crystal field are observed, caused by a pair of impurity ions located close to one another. It is shown that the previously proposed interpretation is incorrect. Fiz. Tverd. Tela (St. Petersburg) 41, 1602–1608 (September 1999)     

二维层状聚合物{[Mn3(btc)(Hbtc)(H2btc)(H2O)6]·6H2O}n的合成

利用蒸气扩散法合成了1,3,5-苯三酸与锰(Ⅱ)的二维层状聚合物{[Mn3(btc)(Hbtc)(H2btc)(H2O)6]·6H2O}n(H3btc=1,3,5-苯三酸).通过X射线单晶衍射、元素分析和红外光谱对其结构进行了表征.中心离子Mn(Ⅱ)处于扭曲的八面体配位环境中,来自btc同一个羧基的两个氧原子,和分别来自Hbtc、H2btc的两个氧原子占据赤道平面,两个配位水的氧原子占据轴向位置.     

Spezifische Wärmen von HoCl3 · 6H2O und ErCl3 · 6H2O im Temperaturbereich zwischen 1,2 °K und 230 °K

Zeitschrift für Physik A Hadrons and nuclei - Die spezifischen Wärmenc Ho undc Er von HoCl3 · 6 H2O und ErCl3 · 6 H2O werden im Temperaturbereich zwischen 1,2 ΩK und 230...     

Crystal structure and Mössbauer spectroscopic study of FeSnF6·6H2O

Large single crystals of FeSnF₆·6H₂O were grown when aqueous hydrofluoric solutions of SnF₂ and FeF₂ were allowed to evaporate in air. Tin-119 Mössbauer spectroscopy at ambient temperature shows a single line at slightly negative isomer shift relative to CaSnO₃ at room temperature (=–0.380(6) mm/s, =0). This is characteristic of tetravalent tin octahedrally coordinated by fluorine. The X-ray crystal structure shows that tin(IV) is coordinated by 6 fluorine atoms, and Fe(II) by 6 water molecules. Both sites show a slight distortion from octahedral symmetry: the six distances are equal (Sn-Fe=1.941(3) Å and Fe-O=2.112(3) Å), whereas there are two values of angles (Fe-Sn-F=90.4(1)° and 89.6(1)°; O-Fe-O=91.1(1)° and 88.9(1)°). The material is an ionic compound [SnF₆]^2–[Fe(H₂O)₆]²⁺.     

改性CaCl2·6H2O混合相变蓄热材料的制备与特性

选用碳素材料(C)石墨(Gr)、石墨烯纳米片(GnPs)、多壁碳纳米管(MWCNTs)和SrCl_2·6H_2O (SCH)为改性剂添加至无机相变材料CaCl_2·6H_2O (CCH)中,制备出不同质量分数碳素材料的无机混合相变蓄热材料C/0.2%SCH/CCH,并表征混合相变材料性能。结果表明:混合相变材料液态导热系数随碳素材料质量分数增加均呈线性提高,其中2.0%石墨烯纳米片可将导热系数提高69.35%;XRD谱图表明碳素材料、SrCl_2·6H_2O和CaCl_2.6H_2O之间的混合都为物理作用;DSC结果显示随碳素材料质量分数增加,相变潜热逐渐降低;质量分数4.0%Gr、2.0%GnPs和2.8%MWCNTs将0.2%SCH/CCH 的放热时间分别减少了 18.0%、41.9%和 12.8%;4.0%Gr/0.2%SCH/CCH、2.0%GnPs/0.2%SCH/CCH 和2.8%MWCNTs/0.2%SCH/CCH在经历100次加速热循环实验后,相变潜热分别降至186 J/g、189 J/g和183 J/g左右,仍满足蓄热要求,混合相变蓄热材料具有良好的热循环稳定性。     

多金属氧酸盐α-Na6H[GeW9Fe3(H2O)3O37]·16H2O的合成和光谱

合成了多金属氧酸盐α-Na6H[GeW9Fe3(H2O)3O37]16H2O，通过元素分析、红外、紫外、光电子能谱、极谱和穆斯堡尔谱等手段进行了表征，并讨论和研究了该配合物的谱学性质。     

Incommensurate Phases of the MgSiF6·6H2O Crystals: EPR and Group-Theoretical Studies

The group-theoretical study of the structural phase transition to incommensurate state of MgSiF₆·6H₂O crystals, revealed by the electron paramagnetic resonance (EPR) method, as well as analysis of the EPR results, are presented. The consideration of temperature dependences of Mn²⁺ admixture ion EPR spectrum symmetry and parameters leads to the conclusion that at T _i1 = 370 ± 0.3 K they undergo second-order structural phase transition to incommensurately modulated state, the order parameter of this transition may be the angle of [Mg(H₂O)₆]²⁺ octahedra rotation around crystal C ₃ axis. At temperature decreasing below T _i1 the gradual transformation of plane-wave modulation of lattice displacements into soliton mode occurs, which is interrupted by the first-order phase transition at T _i2 = 343 ± 0.3 K accompanied by abrupt decrease in modulation amplitude. At T _c = 298.5 ± 0.3 K the first-order improper ferroelastic phase transition into monoclinic phase occurs. The group-theoretical analysis of the phase transition at T _i1 in the investigated crystals, carried out for the first time, has shown that the existence of the incommensurately modulated phase is conditioned by the fundamental reasons (presence of Lifshitz invariant). The conclusions of this analysis on the nature of order parameter, the structural motifs of incommensurate phase and the possible character of temperature evolution of the structure are in agreement with the EPR investigation data.     

Study of the structure of FeSiF6·6H2O by EPR and optical spectra

The method for determining the crystalline structure from relevant EPR zero-field splitting and optical spectra data is applied to ferrous fluosilicate (FeSiF₆·6H₂O. The results, consistent with data from Mossbauer and IR magnetic resonance, show that the effective symmetry of the Fe₂₊ site in FeSiF₆·6H₂O is a rhombic distortion rather than a trigonal one (D_3d).     

Synthesis of single crystalline (NH4)2V6O16·1.5H2O nest-like structures

Novel nest-like (NH₄)₂V₆O₁₆·1.5H₂O structures made of nanobelts have been synthesized by a facile hydrothermal approach. The powder X-ray diffraction pattern of the sample reveals the monoclinic crystalline phase of (NH₄)₂V₆O₁₆·1.5H₂O. The scanning electron microscopy images of the sample obtained at 130 °C for 3 days exhibit nest-like morphology. The transmission electron microscopy result reveals that the nanobelts have a smooth surface. The selected area electron diffraction pattern of the nanobelts indicates single crystalline nature. The two major weight losses occur in thermogravimetric analysis which correspond to the removal of water and ammonia molecules. Further, calcination of the (NH₄)₂V₆O₁₆·1.5H₂O product results in the formation of orthorhombic phase of shcherbianite V₂O₅.     

Crystal and magnetic properties of the new copper-sodium borate CuNaB3O6 · 0.842H2O

A new compound CuNaB₃O₆ · 0.842H₂O was grown for the first time. Its crystal structure, magnetic susceptibility, and magnetic resonance properties are presented. It was proposed that CuNaB₃O₆ · 0.842H₂O is a spin-Peierls magnet with the transition temperature T _SP ～ 128 K and a ladder spin structure. The possibility of a structural phase transition at T < T _SP is predicted.     

Magnetic transitions in K2MnCl4·2H2O

Results of (dM/dH) measurements on tetrahedral K₂MnCl₄·2H₂O as a function of temperature and magnetic field, are presented. An antiferromagnetic transition along the tetragonal axis is observed at T_N = (3.05±0.05) K. The H-T magnetic phase diagram was completely determined, and shows the usual characteristics of that of a low anisotropy antiferromagnet. The T = 0 critical fields are compatible with the values H_E = (29.2±0.3) kOe and H_A = (5.9±0.6) kOe for the exchange and anisotropy fields.     

Das Schwingungsspektrum des monoklinen CaSO4·2H2O

The relations between the imaginary part of the optical dielectric tensor in molecular crystals and transitions active in absorption, derived in a preceding paper [1], are experimentally verified by investigating the vibrational spectrum of monoclinic crystals of gypsum. Reflection spectra of precisely oriented crystal sections were recorded using polarized light between 10 000 cm^?1 and 300 cm^?1 at room temperature and at about 15°K. The eigenfrequencies of polar vibrations and the direction and magnitude of transition moments in the crystal are derived from these spectra. These results definitely support the assumption, that the bands observed between 500 cm^?1 and 300 cm^?1 are caused by hindered rotations of the water molecules. The temperature dependence of the spectra of these molecules in the region of the two stretching modes indicates mixing of these states as a result of the crystalline field. Besides this, mechanisms are discussed, which lead to the decay of excited vibrational modes and thus give rise to the observed temperature dependence of the bandwidths.     

Resonanzaufspaltung im Schwingungsspektrum des CaSO4·2H2O

The resonance- or Davydov- or correlationfield-splittings of the vibrational levels of CaSO₄·2H₂O (gypsum) are calculated using the exciton theory ofDavydov. This theory is extended to include the induced polarization of crystalline matter by the electric fields of the transition dipoles. The numerical calculations are based on an experimental determination of the transition dipole moments and on a calculation of the dipole lattice sums by the Ewald method. The results obtained show, that in most cases the assumption of Coulomb interaction between transition dipoles alone does not completely explain the observed splittings. However, the shift of transition frequency with an increasing longitudinally polarized component of a polar crystal vibration can be predicted by this theory within the limits of accuracy of the experimental determination of transition moments.     

Zero-field NMRON in54Mn-MnCl2·4H2O

We have observed NMRON lines for⁵⁴Mn doped into MnCl₂.4H₂O corresponding to ordering by a strong hyperfine field B_N=60.95 (6) T modified by a weak quadrupole interaction of strength P=+0.52 (7) MHz. The reduction of S_Z for the manganese ion is larger than expected. Point-charge estimates of P yield values which are positive, but smaller than the experimental value.     

Magnetoelectric effect and magnetostriction in the paramagnetic piezoelectric NiSO4 · 6H2O

The direct magnetoelectric effect, the magnetostriction, and the magnetic moment in piezoelectric paramagnetic NiSO₄ · 6H₂O single crystals is comprehensively studied over a wide temperature range in magnetic fields up to 14 T for several magnetic field directions with respect to crystallographic axes. At temperatures above 20 K, the magnetoelectric effect is rigorously quadratic in magnetic field over the entire magnetic field range. As the temperature decreases, the region of quadratic behavior shifts toward low fields. To explain the magnetoelectric effect, the contribution of the magnetostriction-induced piezoelectric effect is considered. It is shown that the piezoelectric effect may be neglected at the helium temperature, where the magnetoelectric effect is high, since its value does not exceed 1%. However, the relative contribution of the piezoelectric effect increases to 10% at T = 40 K, where the magnetoelectric polarization decreases strongly. In contrast to the earlier assumption that the magnetoelectric effect is rapidly and fully saturated in fields higher than 3 T, complete saturation is actually not detected even at 14 T.