Structure of nanocrystalline particles of metallic cobalt formed during the reduction of Co<Subscript>3</Subscript>O<Subscript>4</Subscript> oxide

X-ray diffraction is applied to investigate metallic cobalt obtained by the reduction of nanocrystalline particles of Co₃O₄. The particles of metallic cobalt have a high concentration of stacking faults, i.e., violations of the layer packing sequence ABABAB..., which is seen in X-ray diffraction patterns as anisotropic broadening of diffraction peaks. Simulation of the diffraction patterns of α-Co with a different concentration of stacking faults is carried out.     

The determination of the populations of vibrational levels of molecules from electron diffraction data

The application of modern gas-phase electron diffraction for directly determining the populations of vibrational levels is demonstrated for the molecule I₂. It is concluded that, under the conditions of the conventional electron diffraction experiment, a thermal equilibrium can reliably be assumed for a gas jet but at a temperature which can be markedly lower than that of the nozzle. The diffraction results favour a Boltzmann distribution of molecules over the vibrational states.     

Effect of violations of the structure and layer packing on the diffraction pattern of gibbsite and bayerite

Using the simulation method for the diffraction patterns of one-dimensionally disordered materials, the effect of different violations in the layered structure of aluminum trihydroxides (gibbsite and bayerite) on their diffraction patterns is analyzed. The features of the diffraction patterns of a disordered gibbsite sample obtained by intercalation-deintercalation of lithium salts are considered.     

Studies of orientation and structure of crazed matter in polystyrene. II. Electron diffraction measurements

The technique of selected area electron diffraction in the transmission electron microscope is used to examine the degree of orientation of crazed matter. The theories of electron and x-ray diffraction are compared and it is shown experimentally, by comparison with published x-ray results, that it is possible to obtain electron diffraction patterns from uncrazed polystyrene that are reasonably free of both radiation damage and multiple scattering problems. Electron diffraction patterns from crazes show a considerable degree of orientation but otherwise are very similar to those from uncrazed material, showing that crazes have no structure different from that of bulk material. Diffraction patterns are also obtained from thin films drawn to draw ratios of 4.5 and 6 at 90°C. These agree well with published x-ray results from oriented polystyrene but show less anisotropy than the craze diffraction patterns.     

Modeling of scattering on the residual gas in an electron diffraction experiment

The scattering on the residual gas in an electron diffraction chamber is modeled. A comparison with experimental data reveals that is this scattering that may make a major contribution to the extraneous signal inevitably present in the recorded diffraction pattern. Practical recommendations on the development of the electron diffraction apparatus design are given.     

Solid phases of cyclopentane: combined experimental and simulation study

The phase diagram of cyclopentane has been studied by powder neutron diffraction, providing diffraction patterns for phases I, II, and III, over a range of temperatures and pressures. The putative phase IV was not observed. The structure of the ordered phase III has been solved by single-crystal diffraction. Computational modeling reveals that there are many equienergetic ordered structures for cyclopentane within a small energy range. Molecular dynamics simulations reproduce the structures and diffraction patterns for phases I and III and also show an intermediate disordered phase, which is used to interpret phase II.     

Molecular Structure and Spectral Properties of Methionine Sulfone,Product of Methionine Oxidation

Methionine sulfone , a product of complete oxidation of sulfur in methionine amino acid, was subjectedto X-ray diffraction study on a single crystal. According to X-ray diffraction data the packing of methioninesulfone molecules in a crystal is characteristically strongly anisotropic and it is stabilized by a network of intermolecularhydrogen bonds.     

Structural features of finely dispersed pseudoboehmite obtained by a sol-gel method

Simulation of diffraction patterns, radial distribution function analysis, and electron microscopy are applied to study the features of the structure of nanosized pseudoboehmite obtained by the sol-gel method. It is found to consist of plate-like particles with a thickness of one lattice constant in the [010] direction. Such a structure of the pseudoboehmite particles results in the absence of the 020 diffraction peak in the diffraction pattern.     

The recent development of neutronic techniques for determination of residual stresses

Neutron diffraction is a well-established non-destructive method for the measurement of residual stress deep inside materials. This paper gives a short overview of the use of neutrons for materials research and measurement techniques. Neutron diffraction has been applied in determining residual stresses in metal matrix composites. Measurement and prediction of residual stress for plastic deformation are presented. More recently, the neutron diffraction technique has also been applied for the determination of plastic strain which results from microstructural defects and leads to peak broadening. Influence of the shot penning treatment on austenitic steel is presented.     

Study of X-ray diffraction patterns in Langmuir-Blodgett films using the few-slits model of diffraction

Multilayer films of cadmium 22-tricosenoiate were deposited by using the Langmuir-Blodgett technique in the Z-mode of deposition. The films were then irradiated with various γ-irradiation doses. Small-angle X-ray diffraction patterns of the films before and after γ-irradiation were studied by applying the model of diffraction by a few slits. The X-ray diffraction patterns of the films before γ-irradiation show nine equidistant peaks, indicating the presence of a regular periodic structure in the film. The intensities of the even-order diffraction peaks are relatively less than those from the neighbouring odd-order peaks. This phenomenon, known as even-odd intensity oscillation, was successfully explained by this model. The position of the X-ray diffraction peaks taken for films after different γ-irradiation doses does not change, indicating that the average spacing in the film is unaffected by γ-irradiation. However, the intensity of the diffraction peaks of the film does change with γ-irradiation dose. This change can be explained by the change of electron density along the molecular chain in the layer before and after various γ-irradiation doses.     

In-plane and out-of-plane diffraction of H2 from Ru(001)

H(2) diffraction from the Ru(001) surface has been measured for incident energies E(i) = 78-150 meV and incident angles Θ(i) = 22.1-64.1°. In-plane and out-of-plane angular distributions were measured for incidence along [110] and [100] directions. Out-of-plane diffraction channels were found to be predominant for the explored experimental conditions regardless of the incidence direction. An analysis of diffraction intensities reveals that diffraction out of the scattering plane is enhanced for high incidence angles. Diffractive transitions with wavevector change in the surface plane and transversal to the incidence direction ΔK(⊥) were observed to be favored among the out-of-plane diffractive transitions. These features could be reproduced by model calculations of diffraction intensities performed using a three-dimensional soft potential. This suggests that a kinematic effect is responsible for the large out-of-plane intensities observed in experiment, more than any other features of the six-dimensional H(2)-surface interaction potential.     

铁钼粉末冶金抗磨材料次表面亚稳相的XRD分析

在一台普通的二圆X射线衍射仪上，利用不对称布拉格反射STD（试样相对于入射线倾斜在某一角度α0，进行2θ扫描）技术与常规CBD（正常的θ/2θ偶合扫描）模式相结合的方法，对铁钼粉末冶金抗磨材料的摩擦表层、次表面层及体相的物相纵向进行了较全面分析，特别揭示了摩擦次表面层Fe-C亚稳相的存在，对材料的摩擦性能有严重影响。     

Structural characteristics of nanomaterials based on CdS quantum dots

CdS nanoparticles with sizes where a quantum-size effect is observed are structurally characterized in a detailed way. The following complex of structural methods is used to characterize the nanoparticles: electron diffraction; analytical, diffraction, and high-resolution transmission electron microscopy; and small-angle X-ray scattering.     

The Crystal Structure of Orthocetamol Solved by 3D Electron Diffraction

Orthocetamol is a regioisomer of the well‐known pain medication paracetamol and a promising analgesic and an anti‐arthritic medicament itself. However, orthocetamol cannot be grown as single crystals suitable for X‐ray diffraction, so its crystal structure has remained a mystery for more than a century. Here, we report the ab‐initio structure determination of orthocetamol obtained by 3D electron diffraction, combining a low‐dose acquisition method and a dedicated single‐electron detector for recording the diffracted intensities. The structure is monoclinic, with a pseudo‐tetragonal cell that favors multiple twinning on a scale of a few tens of nanometers. The successful application of 3D electron diffraction to orthocetamol introduces a new gold standard of total structure solution in all cases where X‐ray diffraction and electron‐microscope imaging methods fail.     

Experimental evidence of dynamic trapping in the scattering of H2 from Pd(110)

We have performed H2(D2) diffraction experiments on a Pd(110) surface using two different high-sensitivity set-ups. We have found that, although the total reflectivity of Pd(110) is comparable to that observed in other reactive systems, the corresponding H2(D2) diffraction patterns are quite different: no diffraction peak, including the specular one, is observed on Pd(110). This unexpected result is the consequence of dynamic trapping. Such interpretation is supported by classical dynamics calculations based on accurate ab initio potential energy surfaces.     

Applications of temperature-resolved diffraction methods in thermal analysis

Fundamentals and fields of application of time- and temperature-resolved diffraction methods are presented. X-ray diffraction and neutron diffraction will be considered. Dynamic diffraction methods are increasingly applied in different fields like solid state reactions, heterogeneous catalysis and biological sciences. New methods like synchrotron radiation and position-sensitive detectors permit a considerable expansion of potential research areas. The dynamic diffraction methods are compared with the classical thermoanalytical methods thermogravimetry and DSC.     

X-ray diffraction studies of imperfect crystals by the example of fluorinated graphites

An X-ray diffraction technique for the study of imperfect crystals of natural graphite and its fluorinated products is proposed. The diffraction patterns measured are free from the preferred orientation effect and provide the simulation based on a 1D disordered crystal.     

ChemInform Abstract: Molecular Structure of Chromium Tetrafluoride in the Gas Phase

is determined by electron diffraction at 195-220 °C. The diffraction patterns are completely consistent with a molecule of tetrahedral (Td) symmetry.