三硼酸锂晶体的生长形态

用自由生长系统研究了三硼酸锂ＬｉＢ_３Ｏ_５（ＬＢＯ）晶体的实际生长形态。实验表明，它的各晶面簇的重要性的顺序为：｛１１０｝＞｛０１１｝＞｛２０１｝＞｛１１１｝。讨论了ＬＢＯ晶体的生长习性与内部结构之间的关系并应用负离子配位多面体理论模型解释了ＬＢＯ晶体的生长形态。     

Growth and morphology of single crystals of linear aliphatic polyesters

In order to elucidate the relations between morphological habits and chemical structure of polymers, poly(ethylene sebacate), poly(hexamethylene sebacate) and poly(decamethylene 1,16-hexadecanedicarboxylate) were crystallized from dilute solutions in n-hexanol, isoamyl acetate etc., and were studied with the electron microscopy and x-ray diffraction. The crystal structure of these polyesters are tentatively determined. Morphological “regularity” and “simplicity” of the single crystals are correlated with the chemical structure of the polymers. The crystallization conditions under which “regular” and “simple” single crystals are obtained are relaxed with increase of methylene sequence length in chemical repeat unit. The Bragg extinction bands in the single crystals of poly(hexamethylene sebacate) and poly(decamethylene 1,16-hexadecanedicarboxylate) suggest nonplanar nature of these crystals. The molecular chains in the poly(ethylene sebacate) single crystals are inclined from the normal of the basal plane; the fold surface corresponds to the (001) plane.     

热处理对聚己二酸丁二醋多晶结构和降解行为的影响

通过熔融结晶并结合退火处理方法得到多晶结构的聚己二酸丁二酯(PBA)及具有不同热历史的热力学稳定的a晶型,采用广角X射线衍射仪(WAXD)、原子力显微镜(AFM)和差示扫描量热仪(DSC)研究了PBA的多晶结构、晶体尺寸和结晶形貌,跟踪了退火处理PBA的生物降解行为.结果表明,分子链在相同晶格排列中围绕c轴空间取向的不...     

Characterization of crystal structure in binary mixtures of latex globules

Colloidal crystals formed by two types of polystyrene particles of different sizes (94 and 141 nm) at various number ratios (94:141 nm) are studied. Experiments showed that the formation time of crystals lengthens as the number ratio of the two components approaches 1:1. The dependence of the mean interparticle distance (D₀), crystal structure and alloy structure on the number ratio of the two types of particles was studied by means of Kossel diffraction technique and reflection spectra. The results showed that as the number ratio decreased, the mean interparticle distance (D₀) became larger. And the colloidal crystal in binary mixtures is more preferably to form the bcc structure. This study found that binary systems form the substitutional solid solution (sss)-type alloy structure in all cases except when the number ratio of two types of particles is 5:1, which results instead in the superlattice structure.     

The effect of nitric acid (HNO3) on growth,spectral, thermal and dielectric properties of triglycine sulphate (TGS) crystal

The effect of nitric acid (HNO₃) addition on the growth of triglycine sulphate (TGS) crystal has been studied from the aqueous solution for various concentrations of nitric acid. Significant changes in the crystal size and morphology have been observed in all the grown samples. Single crystal and powder X-ray diffraction analyses confirm the structure and cell parameter values of pure and HNO₃ doped TGS crystals. FT-Raman and FTIR spectra confirm the characteristics absorption bands of pure and HNO₃ doped TGS crystals. The composition of TGS crystals have been confirmed by CHNS analysis. Physical properties such as thermal, dielectric and mechanical studies have been performed for the pure and HNO₃ doped TGS crystals. The dielectric constants of the crystals have been studied as a function of frequency. The results suggest that the HNO₃ is doped into TGS crystal and that the doping increases its dielectric constant.     

BAND STRUCTURE OF BePb–V2 PNICTIDES: AB INITIO CALCULATIONS

Journal of Structural Chemistry - The electronic structure of BePb–V2 crystals (V = N, P, As, Sb) with chalcopyrite structure is studied. The energy band structure and...     

Lamellar structure of poly(ethylene oxide) molecular complexes

The phase diagrams of some binary systems such as poly(ethy lene oxide)-p-dihalogenobenzene, poly(ethylene oxide)-resorcinol and poly(ethylene oxide)-p-nitrophenol show the existence of molecular complexes with a well definite stoichiometry. The crystal structure of these molecular complexes has been determined by wide-angle X-ray diffraction. The morphology of these molecular complexes crystallized from the melt is investigated by differential scanning calorimetry and small angle X-ray scattering. PEO-p-dichlorobenzene and PEO-resorcinol complexes crystallize from the melt as extended chains (EC) or integral folded chain (IFC) lamellar crystals. As observed for PEO oligomers, the fraction of EC crystals of PEO-resorcinol increases with the crystallization temperature. However EC crystals are present in a larger range of crystallization temperatures than for pure PEO. On the other hand, the PEO-p-nitrophenol complex crystallizes over all the studied crystallization temperature range as stable non integral folded chain (NIFC) crystals. Explanations related to the crystal structure of these complexes and to their mode of growth are invoked to explain these two deeply different lamellar morphologies.     

The defect structure of V4As3

The nature of the defect structure of crystals of V₄As₃ has been studied by electron diffraction and electron microscopy methods. Lattice images reveal that planar defects of the chemical twinning type are common in the orthorhombic α-V₄As₃ crystals. Thermal decomposition, yielding negative crystals, was also studied.     

Energy band genesis from sublattice states in MgSiN2 and MgGeN2 crystals

The electronic structure of MgSiN₂ and MgGeN₂ orthorhombic crystals and their sublattices was analyzed at the density functional theory level using the sublattice method. The energy-band structure of the orthorhombic crystals is compared to the structure of their hypothetic analogues with the chalcopyrite lattice. The origin of the specific features of the valence band structure from the sublattice states is determined in the studied crystals, which is mainly due to the interaction of atoms in SiN₄ and GeN₄ cation tetrahedra.     

Structures of deoxypeganine salts

The structures of deoxypeganine (DOP) hydrochloride and oxalate were solved by x-ray structure analysis. An infinite chain along the crystallographic c axis was formed in the crystal structure of DOP oxalate. A molecular framework consisting of Cl anions and DOP cation protonated at N1 was found in the structure of unhydrated DOP hydrochloride. The molecular packing of the “host” (DOP cation) was pseudoisostructural in the studied ion-molecular crystals but differed from other known DOP salts. The “guest” molecules (acid anions) in the studied and known DOP salts formed different intermolecular contacts. __________ Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 280–283, May–June, 2006.     

Growth and optical properties of CuIn7Se11 single crystals

Homogeneous single crystals of CuIn₇S₁₁ having diameters of ～14 mm and ～40 mm long were grown by the vertical Bridgman technique. The composition and structure of the single crystals were determined. Transmission spectra in the region of the intrinsic absorption edge were studied In the single crystals at temperatures in the range from 20 to 300 K. The transmission spectra were used to determine the bandgap width and its value as a function of temperature. Photoluminescence spectra of the crystals were studied in the range from 20 to 130 K. The nature of photoluminescence bands is discussed.     

A study of crystal structure and surface chemistry of silicalites

Crystal structure and sorption properties of silicalites, a new microporous crystalline silica, have been studied. The low temperature phase transition of silicalite into α-cristobalite is detected as being promoted by alkali cations. Removal of alkali cations by acid treatment results in higher thermo-stability of the crystals (to over 1150°C) without any change in maximum sorption capacity for n-hexane. Hydroxyl modes are found to be similar between silicalite and isostructural zeolite and were spectroscopically identified (the band at 3680 cm⁻¹) as hydrolyzed sodium-silicate bonds forming on acid treatment and washing the precursor crystals with water.     

Solid-state polymerization of diacetylenes under the action of outside forces on crystalline monomer lattice

The polymerization of crystalline diacetylenes TS and DCH with different lattice structure was studied under high hydrostatic pressures (up to 4 kbar). It was shown that pressure increases the deformation of chain growing in monomer crystal. The features of such deformation depend on lattice structure that governs the influence of pressure on polymerization rate. We studied also polymerization of diacetylene HD crystals obtained in the pores of stretched polymer (PP). The field of polymer matrix influences the crystal state and the rate of polymerization. It was shown that the interaction of monomer crystals with the matrix leads to growth of more strained chains in these crystals.     

Morphology and fold length of single crystals in linear aliphatic polyesters

The marked effects of chemical structure on the morphology of single crystals in linear aliphatic polyesters have been investigated. Drawn fibers and solution-grown crystals of poly(ethylene sebacate), poly(hexamethylene sebacate), and poly(decamethylene 1,16-hexadecanedicarboxylate) have been studied by small-angle and wide-angle x-ray diffraction. Electron microscopy, and broadline NMR provided supplementary information. The crystal disorder due to irregularity in the cross section of the molecule due to ester groups along the chain direction increases with increase of the methylene sequence length in the chemical repeat unit. On the basis of the x-ray data and electron microscopy, it is proposed that the nature of the fold surface of single crystals of a given polymer, especially a choice of (001) or (hkl) fold surface (flat lamellae or hollow pyramidal crystals), is determined by energetic competition effects between fold geometry and unit cell symmetry. A smooth increase of the long period with increasing crystallization and annealing temperature seems to be general behavior even when a pronounced stepwise increase might be anticipated.     

Effect of aggregation on the excited-state electronic structure of perylene studied by transient absorption spectroscopy

The effect of aggregation on the excited-state electronic structure of perylene was studied through transient absorption measurements of isolated molecules, excimers, monomeric crystals (beta-perylene), and dimeric crystals (alpha-perylene). Changes of electronic state were clearly identified from the changes in transient absorption spectra. A detailed investigation was made by combining the obtained results with previous measurements of ground-state absorption and fluorescence spectra. The energy level of the ion-pair state in alpha-perylene crystals was estimated, and the results are compared with previous photoconductivity results. Moreover, the relaxation processes of excited states in alpha-perylene crystals were studied by femtosecond transient absorption measurements.     

A systematic experimental study of the vO—H…O and vO—D…O in bands of the H bonds of HCOOH and DCOOD crystals

The lineshape of the band corresponding to the stretching vibration v_O—H…O of the H atom in the H bonds of HCOOH crystals (and v_O—D…O in DCOOD crystals) is studied at various temperatures ranging from liquid helium temperature to?25°C. The complex structure of this band is analyzed in terms of elementary bands and a decomposition of the spectrum is proposed. This decomposition will be theoretically analyzed in a subsequent article.     

Crystal structure and morphology of poly(16-hexadecalactone) chain-folded lamellar crystals

Solution-grown, chain-folded lamellar crystals of poly(16-hexadecalactone) (PHDL) were crystallized isothermally from 1-hexanol at 70 degrees C. The morphology of lozenge-shaped crystals was studied by TEM and AFM. The lamellae are ca. 10 nm thick and the chains run orthogonal to the lamellar surface with folding along (110) and (110) planes. The crystal structure of PHDL was determined by XRD and election diffraction of single crystals. The chains are in the 2(1) helix conformation close to all-trans and the structure consists of an orthorhombic unit cell with a P2(1)2(1)2(1) space group with the lattice constants a = 0.746 +/- 0.001 nm, b = 0.504 +/- 0.001 nm, and c (chain axis) = 4.116 +/- 0.003 nm. There are two chains per unit cell, which exist in an antiparallel arrangement. Molecular packing structure has been studied in detail, taking into account both diffraction data and energy calculations. The setting angles, with respect to a axis, were +/-40 degrees for the corner and center chains, respectively. By using the electron and XRD data, the best molecular packing model was refined to R-factors of 0.168 and 0.196, respectively. A brief comparison of chain-packing structure is also made with related polymer structures.     

Impact sensitivity of crystalline phenyl diazonium salts: A first‐principles study of solid‐state properties determining the phenomenon

Two crystalline salts, phenyl diazonium chloride ( PDC ) and tetrafluoroborate ( PDT ), were chosen as probes for theoretical study of solid‐state properties responsible for impact sensitivity since these salts differ only in the nature of anion and, hence, in the properties of solid state. In the present report, we have studied the influence of electronic structure, vibrational spectra, mechanical properties, crystal growth morphology, and the stored energy content on impact sensitivity of PDC and PDT to find the most important solid state characteristics governing this phenomenon. The band structure calculations at various external pressures indicate very different response of the band gap. Extremely sensitive PDC crystals acquire the metallic nature at 29 GPa (metallization point), whilst in the PDT crystals the complete closure of band gap occurs only at 200 GPa. Moreover, the stored energy content in PDC is by 1000 kJ mol^?1 higher than that of PDT . Only these two properties among the calculated in the present work differ significantly in the studied crystals. The rest solid‐state characteristics such as crystal packing, vibratial spectra (phonon‐valence vibration energy transfer probability), elastic properties (bulk moduli) demonstrate rather close values. The influence of metallization point (GPa) as well as crystal growth morphology on impact sensitivity is discussed for the first time.     

1D lead iodide crystals encapsulated within single walled carbon nanotubes

The structure and binding energies of lead iodide crystals encapsulated within single‐walled carbon noanotubes are studied using density functional theory. Calculations were performed on the simulated PbI₂ structure encapsulated within a (12,12) single‐walled nanotube, to investigate the perturbations on the PbI₂ crystal and tube structure and electronic structure, and to estimate the binding energy. The calculation confirms the structure as a single chain of PbI₆ octahedra bound by two chains of PbI₅ square pyramids. The calculated binding energy shows that the encapsulation is noncovalent. Minimal charge transfer is observed between nanotube and the PbI₂ crystals. The band gap is shown to increase from the bulk to the encapsulated structure. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2009     

含有十二烷基酚聚氧乙烯(10)醚的溶致液晶体系的研究

本文以非离子表面活性剂十二烷基酚聚氧乙烯(10)醚(TX-10)/苯乙烯/水组成的三元体系为研究对象, 绘制了三元相图, 选取液晶区域作为研究对象, 配制系列样品, 摄制了纹理照片, 用小角X光衍射法测定了液晶中各种组分变化时间的层间距, 并结合^2H NMR谱图和纹理照片的对照以及互为补充的分析, 为精确区分液晶结构提供了新的途径。这不仅对于基础理论研究, 同时对于日用化工和帮次采油都具有一定指导意义。