Growth and EBSD determination of Celestite SrSO4 dendrites

In this paper, the SrSO₄ dendrites were prepared by diffusion method. Electron backscattered diffraction (EBSD) technique is used to determine the crystallographic orientations of SrSO₄ dendrites. It is shown that the SrSO₄ dendrites grow in (001) plane, and all short main branches grow along <100>, but the long main branches grow along <110>, <130> or <140> directions. The growth morphology of SrSO₄ dendrites is controlled by not only their internal structure but also external growth conditions. The internal structure of SrSO₄ dendrites influences the character of the growth direction vertically <001>. The change of the ions concentration in the diffusion system leads to the evolution from <110> to <140> of the long main branches. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Three‐dimensional thermoelastic stresses in off‐axis oriented single crystals with hexagonal symmetry

A three‐dimensional (3D) thermoelastic stress analysis is carried out on a single crystal with axisymmetric geometry but with a hexagonal crystallographic symmetry. The crystallographic orientation is off‐axis with respect to the cylindrical coordinate system. By applying a Fourier series expansion with respect to the rotational angle ϕ of the cylindrical coordinates, the 3D boundary value problem is reduced to a sequence of 2D ones on the meridian plane, which are solved by the finite‐element method. In our example, the off‐axis orientation is towards a direction of high symmetry, and therefore only four of the six stress tensor components are non‐zero. In the end, the stress tensor is projected onto the slip system of the crystal. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Infinite symmetry applied to crystals and crystal aggregates

Infinite symmetry is referred to for describing in a more rational manner the morphology of certain crystals and crystal, particularly mineral aggregates. Their non-crystallographic forms depend on the peculiarities of their structure, enhanced growth along preferred directions and on the symmetry and composition of the growth environment. Apart from the seven Curie forms others, fitting the corresponding point groups are suitably added as variants of the growth geometry, applicable also to the property of matter.     

Precipitation of intermetallic phase in Zn‐Ti alloy single crystals

Pure and 0.14 at.%Ti alloyed Zn single crystals have been grown by the Bridgman technique. The alloyed crystal exhibits a sheet‐like precipitation structure parallel to the basal plane of the hexagonal solid solution Zn‐Ti matrix. The tetragonal precipitates are intermetallic compounds of Zn₁₆Ti composition. They are needle‐shaped with the needle axis peferentially aligned along the <a> axis. The approximate orientation relationship between precipitate and matrix is (0001)<11$\bar 2$ 0>_Matrix||(010)[001]_Zn16Ti. To study the influence of alloying on the mechanical properties, the critical resolved shear stress for basal slip has been measured in compression at different temperatures and strain rates. It is shown that the critical resolved shear stress can be very well explained by theories of solid solution and precipitation hardening. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

On the capability of revealing the pseudosymmetry of the chalcopyrite‐type crystal structure

The tetragonal crystal‐structure type of chalcopyrites (chemical formula A^IB^IIIC^VI₂) is a superstructure of sphalerite type. The c /a ratio differs generally from the ideal value 2, i.e., the crystal structure is pseudocubically distorted. For CuInSe₂ and CuGaSe₂ thin films, simulations demonstrate that it is theoretically possible to reveal the tetragonality in electron backscatter‐diffraction (EBSD) patterns for CuGaSe₂, whereas it may not be possible for CuInSe₂. EBSD experiments on CuGaSe₂ thin films using the ”Advanced Fit” band‐detection method show that it is possible to extract accurate misorientation‐angle distributions from the CuGaSe₂ thin film. Pole figures revealing the texture of the CuGaSe₂ thin film are shown, which agree well with X‐ray texture measurements from the same layer. (© 2008 WILEY ‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

The crystal and molecular structures of cyclohexanone thiosemicarbazone

Cyclohexanone thiosemicarbazone (Hchtsc) crystallizes in the triclinic crystal system with space group P (No. 2) and the following unit cell parameters: a = 6.2989(2), b = 7.9730(3), and c = 9.4118(2) Å = 79.607(3), = 85.519(2), and = 73.50(2)° V = 445.60(2) ų, Z = 2. The lengths of the bonds C(1)–S, C(1)–N(1), C(1)–N(2), and N(2)–N(3) suggest electron delocalization in all four. The S atom is trans to N(3), and this E configuration is stabilized by intramolecular hydrogen bonding between N(3) and the N(1)H₂ group. Two intermolecular hydrogen bonds involving the S atom and the N(1)–H(1b) and N(2)–H(2) groups give rise to a polymeric chain of molecule pairs.     

Syntheses and crystal structures of two N-substituted thio-imidazoles

The syntheses and structures of two N-substituted thio-imidazoles are reported. The geometrical parameters for both compounds, including essentially planar imidazole rings, are consistent with previous structural studies of related materials. The only possible non-van der Waals’ interactions influencing the molecular packing are weak C–H⋯π bonds. Crystal data: C₁₂H₁₄N₂S (N-methyl-N′-2-phenylethyl-imidazol-2-thione), M _r = 218.31, monoclinic, P2₁/n, (No. 14), a = 6.8441(2) ?, b = 12.9960(4) ?, c = 13.4703(4) ?, β = 97.7729(16)°, V = 1187.12(6) ?³, Z = 4, R(F) = 0.039, wR(F ²) = 0.104. C₁₉H₂₀N₂S (N,N′-bis((s)-1-phenylethyl)imidazol-2-thione), M _r = 308.43, orthorhombic, P2₁2₁2₁ (No. 19), a = 10.4060(3) ?, b = 10.6712(3) ?, c = 14.8932(3) ?, V = 1653.81(7) ?³, Z = 4, R(F) = 0.038, wR(F ²) = 0.085.     

Investigation of orientation relationships by EBSD and EDS on the example of the Watson iron meteorite

The suitability of the electron back‐scatter diffraction technique (supported by EDS) in order to study the complex microstructures of iron meteorites is demonstrated on the example of the Watson meteorite. The orientation relationships between the main phases kamacite, taenite and schreibersite/rhabdite as well as effects of the real structure have been investigated. In kamacite bands highly deformed blocks appear which show a contineous change of orientation. Plessitic regions are surrounded by deformed taenite lamellae. Also these lamellae show the typical M‐profile of the Ni concentration in cross section. In the center a martensitic microstructure has been proven. The white plessite is characterized by a high number of individual kamacite grains which however are separated mainly by low‐angle boundaries. So an orientation clustering occurs. The determination of orientation relationships was only possible for a single plessite region comparing the intensity distribution in pole figures with simulations. Schreibersite is brittle and shows a high number of microcracks. However, the strong deformation of kamacite does not allow us to decide whether an orientation relationship between the phosphides and the surrounding kamacite exists or not. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Influence of solvent and crystallization method on the crystal habit of metronidazole

In the present study, metronidazole was crystallized in several solvents, according to both the “cooling crystallization” and the “crystallization by non‐solvent addition”. Particle properties, such as crystal habit, elongation ratio, and mean particle size, were determined by SEM analysis. Structural changes and development of polymorphic forms were excluded by both Differential Scanning Calorimetry (DSC) and X‐Ray Powder Diffractometry (XRPD). Crystal habit (and thus elongation ratio) was typically influenced by both the solvent polarity index and the crystallization method: solvents with higher polarity index tended to promote acicular or stick‐shaped crystals with a high elongation ratio, while isodimensional crystals were promoted by decreasing the polarity index, as was particle aggregation. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Crystal structure,dielectric properties of (K0.5Na0.5)NbO3 single crystal grown by flux method using B2O3 flux

Lead free piezoelectric single crystals of sodium potassium niobate (K_0.5Na_0.5)NbO₃ (KNN) were grown by high‐temperature solution method using two different fluxes; one with a mixture of NaF and KF and other with addition of B₂O₃ along with the mixture. In the present study, the growth of KNN crystals without B₂O₃ flux and the same with B₂O₃ flux were compared. It was found that additions of small amounts of B₂O₃ lowered the melting temperature of the solid solution and enabled better dielectric properties. Phase analysis showed that all samples were crystallized in pure orthorhombic perovskite phase. AFM morphological studies showed that the addition of B₂O₃ flux increased the roughness of the grown crystal. Further, addition of B₂O₃ flux slightly decreased the orthorhombic to tetragonal phase transition temperature T_(O—T) and the Curie temperature T_C. The ferroelectric behaviour of KNN single crystal has been investigated at room temperature. The crystal grown using B₂O₃ flux exhibited a remanent polarization (P_r) ∼ 32 μC/cm² and coercive field (Ec) of ∼11.8 kV/cm whereas the crystal grown without the use of B₂O₃ flux had a remanent polarization (P_r) ∼ 36 μC/cm² and coercive field (Ec) of ∼14.6 kV/cm.     

Investigation of nucleation kinetics and crystal defects of HMX

The nucleation kinetics of HMX (cyclotetramethylene tetranitramine, C₄H₈N₈O₈) in γ‐butyrolactone was studied in cooling process by induction time method. The laser scattering method was used to measure the solubility data and metastable region of HMX in γ‐butyrolactone. The induction time was measured over a range of supersaturation at different temperatures. Then, the nucleation mechanism of HMX in γ‐butyrolactone was investigated by analysis the relationships between induction time and supersaturation. The results indicated homogeneous nucleation dominated at high supersaturation of S >1.35, while the heterogeneous nucleation dominated at low supersaturation of S < 1.35. The values of interfacial tension at different final temperatures were calculated to indicate the ability of HMX to be crystallized. The growth mechanism of HMX was investigated by the data fitting applying different growth mechanism models and identified as two‐dimensional nucleation‐mediated (2D) growth. Finally, the effects of supersaturation and temperature on the crystal defects were analyzed based on the nucleation kinetics. When the temperature is below 303.15K, homogeneous nucleation dominated the nucleation process at higher supersaturation. Fine HMX crystals with more defects were produced. On the contrary, heterogeneous nucleation mechanism dominated at lower supersaturation. large regular HMX crystals with fewer defects were formed when the temperature is above 318.15K.     

Anisotropic sublattices in cubic perovskite and their symmetry in multidimensional crystal space

Three tetragonal, partially occupied oxygen sublattices with a translational symmetry higher than the lattice translational symmetry can be introduced into the cubic perovskite structure. This higher symmetry is determined in the 9D space constructed on three orthogonal 3D subspaces corresponding to the sublattices. The generating matrices, metric tensors, and point symmetry matrices of this multidimensional space are determined. Irreducible stars of the representations of multidimensional space group are projected onto the irreducible stars of the space crystal group.     

High temperature synthesis and crystal structure of new representatives of the huntite family

Single crystals of REE, Al borates, new and known representatives of huntite family are obtained by annealing of REEBO₃ on Al₂O₃ surface at 1100°C. Phase identification for REE=Pr, Eu, Tb, Tm, Ho, Yb has been carried out using unit cell parameter determination on single crystals. Crystal structures of C 2/c (PrAl₃(BO₃)₄) and C 2 (EuAl₃(BO₃)₄) ‐ two polytypic modifications, previously determined for other REE's have been studied. Formation of one or another polytype in similar thermodynamic conditions is probably dependent on electronic structure of rare earth ion. Crystal field stabilization energy in crystal fields of different symmetry is a possible factor of polytype stability (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

水热法合成氧化锌晶体

本文采用水热法,通过改变矿化剂浓度,合成了具有不同晶体形态的氧化锌晶体.在430℃,填充度为35;,矿化剂浓度为1M KOH时,只合成了氧化锌微晶.氧化锌晶体的长度为几百纳米到几微米,晶体形状为六棱锥体.当矿化剂为3M KOH或2M KOH、1M KBr时,合成了高质量的氧化锌晶体.反应 24h后,合成的最大晶体长度(c轴方向)超过1mm,晶体呈单锥六棱柱体,显露柱面m{1010}、锥面p{1011}、负极面o面{0001}.另外还生成多种不同形态的微晶体,最小几微米,中等的几十微米,为六棱锥体,显露锥面p{1011}、负极面o面{0001},没有显露柱面.     

Tautomeric investigations and crystal structure analysis of chlorzoxazone

The crystal structure and infrared spectra of the compound has been reported. Infrared spectra of the compound were examined in various solvents. The results of the crystal structure analysis and IR spectra assignments showed that the compound has the amino tautomeric form in the solid state and in studied solutions.     

X-ray crystal structural analysis of dicyclohexylthiocarbamide

The title compound dicyclohexylthiocarbamide has been determined by single crystal X-ray crystal diffraction analysis. The crystals are monoclinic, space group P2(1)/c with a = 12.5908(9), b = 11.2158(9), c = 10.4255(8) Å, α = 90, β = 110.7360(10), γ = 90°, V = 1376.88(18) ų, Z = 4, F(000) = 528, D_c = 1.160 g/cm³, μ = 0.214 mm^?1, the final R = 0.0381 and wR = 0.1030. A total of 6836 reflections were collected, of which 2423 were independent (R_int = 0.0154). In the crystal packing diagram, intermolecular N?H···S hydrogen bonds stabilize the solid state of the title compound.     

Combination of colored patterns and cubes for crystallographic point group visualization

A concept based on the application of a cube as a general polyhedron is presented for the visualization of point group symmetry. The cube is used to represent both the highest and lowest crystal symmetries, with differences observable as patterns characteristic to each point group. Patterns are generated using direction‐specific color keys, which enable the recognition of point group‐specific distribution of vectors in an external reference frame. For the visualization of the incoherent hexagonal crystal classes, two twinned cubes are applied in order to generate symmetry operators that would otherwise be missing. The resulting hexagonal dipyramid is described in the frame of a cube, reducing the number of used symmetry operators from 72 to 60. The complete set of 32 polyhedra are suitable, for example, as a visual aid for understanding the crystal symmetry and/or sub‐ and supergroup relationships.     

Synthesis and crystal structure of tripeptide fragment of elastin

Boc-Gly-Val-Pro-OBzl, a protected tripeptide fragment of repeating sequences of mammalian elastic protein elastin was synthesized and characterized by X-ray diffraction method. The sequence C₂₄ H₃₅ N₃ O₆ crystallizes in the orthorhombic space group P2₁2₁2₁ with the parameters a = 9.4700(11) Å, b = 9.8980(8) Å, c = 26.721(3) Å, V = 2504.7(4) ų and Z = 4. The final residual factor is 0.0670. The structure exhibits intra and intermolecular hydrogen bonds.