X-Ray Diffraction Studies on Molecular Semiconductors Based on Charge-Transfer Complexes of Substituted Phenothiazines with 2,3-Dichloro-5,6-dicyano-p-benzoquinone

X-ray powder diffraction data on the molecular semiconductors based on the 1:1 charge-transfer complexes of the electron donors, viz. phenothiazine (PTZ), 2-chlorophenothiazine (CPZ), 2-acetyl phenothiazine (APZ) and 2-(trifluoromethyl)-phenothiazine (TPZ) with 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ) have been reported in this paper. The indexing has been done by Ito's method. All the complexes have been found to have orthorhombic crystal structures. The lattice parameters for the individual complexes are as follows: (i) PTZ-DDQ: a = 6.020 Å, b = 9.775 Å, c = 24.280 Å; (ii) CPZ-DDQ: a = 5.830 Å, b = 8.070 Å, c = 20.280 Å; (iii) APZ-DDQ: a = 5.055 Å, b = 7.955 Å, c = 19.520 Å; (iv) TPZ-DDQ: a = 5.130 Å, b = 8.195 Å, c = 19.850 Å.     

High-Pressure X-ray Diffraction Studies on Organic Crystals

The high-pressure X-ray diffraction technique, commonly applied for inorganic crystals, is discussed in a view of its application for laboratory studies on molecular crystals of organic compounds – particularly when the weak X-ray scattering of such specimens causes experimental difficulties. To minimize the background-to-signal ratio, relatively big crystal samples (ca. 0.005 A³) were used and the mechanical properties of the gasket material were applied to obtain the optimum experimental conditions for pressure generation and lowering the background of reflections. The mechanical properties of tungsten, Inconel, and hardened steel gaskets are different and these properties can be helpful in planning high-pressure measurements with large high-pressure chamber to contain a big crystal sample. Several characteristic features of organic crystals – like their strong compressibility (depending on the nature of intermolecular interactions) and pressure-dependence of thermal vibrations of atoms – can have a direct impact on the conditions of high-pressure experiments. The properties of molecular crystals of organic compounds have been discussed on the basis of several high-pressure structural studies, mainly on simple cyclic β-diketoalkanes (enol forms). It has been attempted to assess the feasibility of investigating the details of molecular structure at high pressures by X-ray laboratory studies. A systematic pressure-induced change in the length of double C  O bonds is observed in this group of compounds, which can be correlated with the compression of the H-bonds involving the carbonyl groups.     

DTA,DSC, and X-ray Powder Diffraction Studies on Some Zinc Selenate Hydrates

The thermal dehydration of ZnSeO₄ · 6 H₂O, ZnSeO₄ · 5 H₂O, and ZnSeO₄ · 3 H₂O has been studied by TG, DTA, and DSC-analyses. It has been established that the dehydration of ZnSeO₄ · 6 H₂O occurs stepwise and as intermidiate hydrates ZnSeO₄ · 5 H₂O, ZnSeO₄ · 3 H₂O and ZnSeO₄ · H₂O are produced. The enthalpy of dehydration of the observed phase transitions has been determined. The enthalpy of formation of ZnSeO₄ · 6 H₂O, ZnSeO₄ · 5 H₂O, ZnSeO₄ · 3 H₂O, and ZnSeO₄ · H₂O has been calculated on the basis of the DSC-data. ZnSeO₄ · 5 H₂O and ZnSeO₄ · 3 H₂O have been studied rentgenographically: ZnSeO₄ · 5 H₂O crystallizes in triclinic system with lattice parameters: a = 6.387(2) Å; b = 10.706(3) Å; c = 6.167(3) Å; α = 98.66(2)°; β = 109.32(3)° γ = 75.52(3)° V = 384.3(2) ų; SG P1 . ZnSeO₄ · 3 H₂O forms orthorhombic crystals with lattice constants: a = 8.165(4)Å; b = 11.314(5) Å; c = 12.465(7) Å; V = 1151.5(7) ų; SG Pbca.     

Some Physicochemical Studies on Binary Organic Eutectics and 1:2 Molecular Complexes

Benzidine-m. aminophenol system gives a double simple eutectic type phase-diagram showing the formation of a 1:2 addition compound with congruent melting point surrounded by two eutectics on either side. The linear velocity of crystallization data on pure components, eutectics, and addition compound suggest square relationship between growth velocity and undercooling. From the X-ray diffraction studies it can be inferred that the eutectics are not a simple mechanical mixtures of two components. Whereas microstructural investigations suggest faceted growth of the addition compound and a typical characteristic growth of the eutectics, spectral studies indicate the formation of intermolecular hydrogen bonding between two components forming the molecular complex.     

X-ray Diffraction and DFT Studies of 2-Methoxy-5-phenylaniline

Abstract 2-Methoxy-5-phenylaniline, a promissor monomer for PANI studies, has been characterized by single-crystal X-ray diffraction at two temperatures: orthorhombic, space group P2₁2₁2₁, Z = 12 with a = 5.9900(2) ?, b = 20.4873(6) ?, c = 26.3727(8) ? and R = 0.0868 for 293(2) K and a = 5.8337(9) ?, b = 20.4428(31) ?, c = 26.0773(40) ? and R = 0.0669 for 120(2) K. There are three independent molecules in the unit cell. One of them is approximately planar, the other two have the phenyl rings rotated. At room temperature the two latter molecules are joined in dimers through H-bonds and at low temperature the same molecules are joined in columns that run along the a-axis. Index Abstract X-ray Diffraction and DFT Studies of 2-Methoxy-5-phenylaniline Ana T. Marques, Joana A. Silva, Manuela Ramos Silva, Ana Matos Beja, Licinia L. G. Justino, Abilio J. F. N. Sobral 2-Methoxy-5-phenylaniline, a promissor monomer for PANI studies, has been characterized by single-crystal X-ray diffraction at 293(2) K and 120(2) K. The three independent molecules in the unit cell show different conformations and establish distinct intermolecular H-bonds.      

人造金刚石晶体缺陷的同步辐射X射线衍射形貌像浅析

利用同步辐射X射线对人造金刚石晶体缺陷进行了形貌学研究,实验采用了透射(劳埃)形貌术和反射形貌术两种方法.所得的X射线透射劳埃图上大部分斑点分别分布在四条主晶带上,经分析发现,该金刚石晶体主要的晶体缺陷为位错,并推导出晶体内部存在Frank不全位错.该晶体的反射形貌像中位错呈网状分布,说明其表层缺陷多于内部缺陷.此外,由形貌像分析发现该人造金刚石晶体的晶体缺陷明显少于天然金刚石.     

Stereochemical Assignment of Substituted 2-Aminobicyclo[3.1.0]hexane and 2-Aminobicyclo[5.1.0]octane Derivatives via Single Crystal X-ray Diffraction

Abstract  

Crystals of benzyl (RS,RS,RS)-7-phenylbicyclo[5.1.0]octan-2-ylcarbamate 9 and (RS,RS,RS)-N-[3′-(4″-methylpiperazin-1″-yl)propyl]-N-{5-(4′′′-cyanophenyl)bicyclo[3.1.0]hexan-2-yl}amine dihydrochloride 10·2HCl were synthesised and single crystal X-ray diffraction was used to establish unambiguously the relative configurations within these structures. Compound 9 crystallizes in the orthorhombic space group P2 ₁ 2 ₁ 2 ₁ with cell parameters of a = 6.85340(10) ?, b = 9.8732(2) ?, c = 27.5407(6) ?, V = 1863.54(6) ?³ and Z = 4. In the crystal structure adjacent molecules are linked by N–H···O=C hydrogen bonds. Compound 10·2HCl crystallizes as the corresponding monohydrate in the monoclinic space group P2 ₁/n with cell parameters of a = 7.1540(17) ?, b = 39.763(12) ?, c = 8.163(3) ?, β = 91.062(7)°, V = 2321.7(11) ?³ and Z = 4. In the crystal structure adjacent molecules are linked by a series of hydrogen bonds between the ammonium groups, chloride ions and adventitious water molecules.     

X-ray Diffraction Analysis and Electron Microscopy of the Carbon Fiber Structure

Crystallography Reports - A technique for studying the carbon-fiber structure using X-ray diffraction and electron microscopy has been developed. Average crystal-structure parameters are determined...     

X-ray Diffraction Study of Structural Changes in High-Strength Ceramics Based on Zirconium Oxide with Additions of Ytterbium and Neodymium Oxides after Hydrothermal Treatment

Crystallography Reports - A surface structural analysis of two ceramic samples of zirconium oxide (ZrO2) sintered at 1550°C, stabilized in the tetragonal form, before and after hydrothermal...     

Simultaneous X-Ray Diffraction and Differential Scanning Calorimetry (XDDSC) in Studies of Molecular and Liquid Crystals

The technique of simultaneous X-ray diffraction and differential scanning calorimetry (XDDSC) is introduced into the field of molecular and liquid crystals. The technique allows fast time-resolved X-ray diffractograms to be recorded simultaneously with the recording of heat flow into or out of the specimen during a heating, cooling or isothermal scan. Structural transformations, as revealed by changes in the diffraction pattern, can thereby be unambiguously correlated with thermal events such as endo-or exo-therms or changes in heat capacity. Small and wide angle diffraction can be monitored. Sample pans and cuvettes made of boron nitride or graphite are used, both materials combining high transparency for X-rays with good thermal conductivity. Selected examples of application of the technique are presented.     

SiC衬底上生长的GaN外延层的高分辨X射线衍射分析

通过高分辨X射线衍射(HRXRD)技术,对金属有机化合物气相外延(MOCVD)生长的GaN外延膜及SiC衬底的相对取向,晶格常数和应力情况,位错密度等进行了分析.分析表明,GaN和SiC具有一致的a轴取向,GaN外延层弛豫度超过90;,GaN外延层的晶格常数与体块材料相近,在GaN中存在压应力,SiC衬底和GaN外延层中的位错密度分别为107和108量级.     

GaAs-GaN键合界面热应力的电子背散射衍射研究

采用扫描电镜(SEM)和电子背散射衍射(EBSD)技术,观察和分析了GaAs和GaN晶片热压键合的界面热应力和晶片键合质量.利用EBSD测量了GaAs-GaN键合界面的菊池花样质量、晶格转动、晶格错配和位错密度等应力敏感参数.结果表明,晶片键合质量良好,键合界面中心区域的热应力小于边缘区域的热应力.GaN层和GaAs层中的应力影响范围,在中心区域分别约为100 nm和300 nm,在边缘区域分别约为100 nm和500nm.EBSD显示的应力分布图与模拟应力场相似.模拟和计算表明,最大剥离应力和剪切应力分布在键合界面的边缘.剥离应力是导致晶片解键合的主要原因.