October 2015 issue
A new approach is presented for an in situ investigation of the microstructures of polycrystalline samples undergoing phase transitions at Earth's mantle pressure and temperature. Diffraction experiments are carried out using synchrotron radiation combined with a resistively heated diamond anvil cell up to 25 GPa and 1000 K. Multi-grain analysis is used to follow phase proportions and grain size distributions, and to track individually hundreds of grains in the transforming sample. As an illustration, results are presented of the evolution of microstructure during the α–γ transition in hydrous Mg2SiO4·H2O up to 22 GPa and 940 K.
Small-angle X-ray scattering is used to determine the shape and periodicity of nanostructures patterned with industrially relevant fabrication techniques.
Thermal expansion tensors and their temperature dependence are derived for a set of 13 energetic materials.
The mosaic crystal highly annealed pyrolytic graphite (HAPG) has been characterized with respect to its diffraction properties using monochromated synchrotron radiation.
A general theory for elastic scattering from laterally heterogeneous vesicles is presented. The analytical form factor for static round domains provides a new and important tool for the quantitative analysis of neutron scattering data from phase-separated vesicles.
The influence of noncentrosymmetric crystal structures on electron backscatter diffraction (EBSD) patterns is analysed using the example of zincblende-structure-type semiconductors. EBSD measurements combined with dynamical theory Kikuchi pattern simulations enable the polarity of lattice planes to be assigned.
A procedure is investigated for calculating single-crystal X-ray thermal diffuse scattering features using a molecular dynamics simulation. The results are compared with experimental observations and the results from previous Monte Carlo simulations.
A study of the atomic structure of multi-layered graphene obtained by chemical exfoliation is described. Wide-angle neutron and X-ray scattering along with computer simulations were used, which yielded a good agreement between the experimental data and the theoretical models.
On the basis of the continuum theory of micromagnetics, the correlation function of the spin-misalignment small-angle neutron scattering cross section of bulk ferromagnets is computed and discussed.
On the basis of simulations, a theoretical concept for the evaluation of strongly inhomogeneous residual stress depth gradients by means of the stress scanning method is presented. Simulations for very small gauge volumes are presented for the energy-dispersive case of diffraction.
The modified stress scanning concept, which was introduced in the first part of this study, is implemented for the analysis of the strongly inhomogeneous residual stress depth distributions present within a bulk material and an alternately stacked multilayer coating system.
Depolarized dynamic light scattering is applied to distinguish between nucleation and amorphous cluster formation in protein solutions during crystallization.
Resolution- and temperature-dependent factors such as thermal diffuse scattering can lead to significant errors in charge density studies. The influence on the model of the crystal structure is shown and a simple empirical correction is proposed.
The analysis of absolute small-angle X-ray scattering measurements reveals that the temperature-dependent density of the liquid-like amorphous phase enclosed between crystalline layers in semicrystalline polyethylene is crystallinity independent and lower than melt-extrapolated values.
A large amount of local strain is found to be accumulated in tetragonal hen egg white lysozyme crystals grown under an applied field at 20 kHz through analysis of the X-ray rocking-curve profile full width at half-maximum. Comparison with previous results obtained for crystals grown with an applied field at 1 MHz suggests that there is an optimum frequency to achieve an improved quality of protein crystals.
A novel neutron spin filter based on the strong spin dependence of the neutron scattering on protons has been developed. Its application as a polarization analyzer is demonstrated in a magnetic SANS experiment with the measurement of the spin-dependent scattering signals of a CuFeNi alloy.
Laue single-crystal and monochromatic powder micro-diffraction mappings are combined to describe the organization of the crystalline phases in archaeological artefacts at the micrometre scale, in relation with the physical properties of these heterogeneous materials.
Information on the shape and size distribution of Pd nanocrystals as well as their surface structure and defects is obtained by combining X-ray diffraction line profile analysis with transmission electron microscopy and surface electrochemistry.
The high-resolution temperature-dependent diffuse X-ray scattering from an Na0.5Bi0.5TiO3 perovskite-based single crystal is measured on the approach to the polymorphic phase transition. The previously unseen topological features of the diffuse scattering and their temperature evolution are reported.
Different crystallization techniques such as vapour diffusion in hanging drops and counterdiffusion in gels allowed the selective isolation of different crystal polymorphs of the SdsA protein from Pseudomonas aeruginosa PAO1 and improved their diffraction quality. Analysis of the three-dimensional structures obtained from the different polymorphs provided insights into the relevance of crystal packing for the interpretation of biological information.
Representational analysis is used to characterize correlated short-range order in large atomistic ensembles. This method, analogous to tight-binding methods, enables the extraction of relevant structural parameters in an orthogonal and local basis that permits robust statistical analysis of crystalline disorder.
Profex is a platform-independent open-source graphical user interface for the Rietveld refinement program BGMN.
AutoFP is distributed freely as a highly automated software toolkit for the widely used Rietveld refinement program FullProf.
A computer program to perform small-angle X-ray and neutron scattering data evaluation is presented.
Evidence is presented that water outgassing from polyimide (Kapton HN-type) capillaries at temperatures as low as 438 K causes the overgrowth of supported Pt catalysts.
Light scattering and small-angle scattering data indicate that for globular proteins the relation between molecular weight and radius of gyration follows a power law which can be related to the fractal dimension of the proteins.