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Journal of Applied Crystallography

Ai Woon Yee, Matthew P Blakeley, Martine Moulin, Michael Haertlein, Edward Mitchell, V Trevor Forsyth
The application of IR spectroscopy to the characterization and quality control of samples used in neutron crystallography is described. While neutron crystallography is a growing field, the limited availability of neutron beamtime means that there may be a delay between crystallogenesis and data collection. Since essentially all neutron crystallographic work is carried out using D2O-based solvent buffers, a particular concern for these experiments is the possibility of H2O back-exchange across reservoir or capillary sealants...
April 1, 2017: Journal of Applied Crystallography
Michael G Bowler, David R Bowler, Matthew W Bowler
The humidity surrounding a sample is an important variable in scientific experiments. Biological samples in particular require not just a humid atmosphere but often a relative humidity (RH) that is in equilibrium with a stabilizing solution required to maintain the sample in the same state during measurements. The controlled dehydration of macromolecular crystals can lead to significant increases in crystal order, leading to higher diffraction quality. Devices that can accurately control the humidity surrounding crystals while monitoring diffraction have led to this technique being increasingly adopted, as the experiments become easier and more reproducible...
April 1, 2017: Journal of Applied Crystallography
Steffen M Sedlak, Linda K Bruetzel, Jan Lipfert
A new model is proposed for the measurement errors incurred in typical small-angle X-ray scattering (SAXS) experiments, which takes into account the setup geometry and physics of the measurement process. The model accurately captures the experimentally determined errors from a large range of synchrotron and in-house anode-based measurements. Its most general formulation gives for the variance of the buffer-subtracted SAXS intensity σ(2)(q) = [I(q) + const.]/(kq), where I(q) is the scattering intensity as a function of the momentum transfer q; k and const...
April 1, 2017: Journal of Applied Crystallography
Thu Nhi Tran Thi, J Morse, D Caliste, B Fernandez, D Eon, J Härtwig, C Barbay, C Mer-Calfati, N Tranchant, J C Arnault, T A Lafford, J Baruchel
Bragg diffraction imaging enables the quality of synthetic single-crystal diamond substrates and their overgrown, mostly doped, diamond layers to be characterized. This is very important for improving diamond-based devices produced for X-ray optics and power electronics applications. The usual first step for this characterization is white-beam X-ray diffraction topography, which is a simple and fast method to identify the extended defects (dislocations, growth sectors, boundaries, stacking faults, overall curvature etc...
April 1, 2017: Journal of Applied Crystallography
Mykhailo Barchuk, Mykhaylo Motylenko, Gleb Lukin, Olf Pätzold, David Rafaja
The microstructure of polar GaN layers, grown by upgraded high-temperature vapour phase epitaxy on [001]-oriented sapphire substrates, was studied by means of high-resolution X-ray diffraction and transmission electron microscopy. Systematic differences between reciprocal-space maps measured by X-ray diffraction and those which were simulated for different densities of threading dislocations revealed that threading dislocations are not the only microstructure defect in these GaN layers. Conventional dark-field transmission electron microscopy and convergent-beam electron diffraction detected vertical inversion domains as an additional microstructure feature...
April 1, 2017: Journal of Applied Crystallography
B K Tanner, A N Danilewsky, R K Vijayaraghavan, A Cowley, P J McNally
Transmission X-ray diffraction imaging in both monochromatic and white beam section mode has been used to measure quantitatively the displacement and warpage stress in encapsulated silicon devices. The displacement dependence with position on the die was found to agree well with that predicted from a simple model of warpage stress. For uQFN microcontrollers, glued only at the corners, the measured misorientation contours are consistent with those predicted using finite element analysis. The absolute displacement, measured along a line through the die centre, was comparable to that reported independently by high-resolution X-ray diffraction and optical interferometry of similar samples...
April 1, 2017: Journal of Applied Crystallography
Andrey Lomov, Kirill Shcherbachev, Yurii Chesnokov, Dmitry Kiselev
The structural changes in the surface layer of p-type Cz-Si(001) samples after high-dose low-energy (2 keV) He(+) plasma-immersion ion implantation and subsequent thermal annealing were studied using a set of complementary methods: high-resolution X-ray reflectometry, high-resolution X-ray diffraction, transmission electron microscopy and atomic force microscopy. The formation of a three-layer structure was observed (an amorphous a-SiO x layer at the surface, an amorphous a-Si layer and a heavily damaged tensile-strained crystalline c-Si layer), which remained after annealing...
April 1, 2017: Journal of Applied Crystallography
Johannes Hagemann, Tim Salditt
This work presents a numerical study of the fluence-resolution behaviour for two coherent lensless X-ray imaging techniques. To this end the fluence-resolution relationship of inline near-field holography and far-field coherent diffractive imaging are compared in numerical experiments. To achieve this, the phase reconstruction is carried out using iterative phase-retrieval algorithms on simulated noisy data. Using the incident photon fluence on the specimen as the control parameter, the achievable resolution for two example phantoms (cell and bitmap) is studied...
April 1, 2017: Journal of Applied Crystallography
Simone Vadilonga, Ivo Zizak, Dmitry Roshchupkin, Emelin Evgenii, Andrei Petsiuk, Wolfram Leitenberger, Alexei Erko
X-ray Bragg diffraction in sagittal geometry on a Y-cut langasite crystal (La3Ga5SiO14) modulated by Λ = 3 µm Rayleigh surface acoustic waves was studied at the BESSY II synchrotron radiation facility. Owing to the crystal lattice modulation by the surface acoustic wave diffraction, satellites appear. Their intensity and angular separation depend on the amplitude and wavelength of the ultrasonic superlattice. Experimental results are compared with the corresponding theoretical model that exploits the kinematical diffraction theory...
April 1, 2017: Journal of Applied Crystallography
Martin Schmidbauer, Michael Hanke, Albert Kwasniewski, Dorothee Braun, Leonard von Helden, Christoph Feldt, Steven John Leake, Jutta Schwarzkopf
Scanning X-ray nanodiffraction on a highly periodic ferroelectric domain pattern of a strained K0.75Na0.25NbO3 epitaxial layer has been performed by using a focused X-ray beam of about 100 nm probe size. A 90°-rotated domain variant which is aligned along [1[Formula: see text]2]TSO has been found in addition to the predominant domain variant where the domains are aligned along the [[Formula: see text]12]TSO direction of the underlying (110) TbScO3 (TSO) orthorhombic substrate. Owing to the larger elastic strain energy density, the 90°-rotated domains appear with significantly reduced probability...
April 1, 2017: Journal of Applied Crystallography
P Scardi, L Rebuffi, M Abdellatief, A Flor, A Leonardi
Synchrotron radiation X-ray diffraction (XRD) patterns from an extensively ball-milled iron alloy powder were collected at 100, 200 and 300 K. The results were analysed together with those using extended X-ray absorption fine structure, measured on the same sample at liquid nitrogen temperature (77 K) and at room temperature (300 K), to assess the contribution of static disorder to the Debye-Waller coefficient (Biso). Both techniques give an increase of ∼20% with respect to bulk reference iron, a noticeably smaller difference than reported by most of the literature for similar systems...
April 1, 2017: Journal of Applied Crystallography
Wojciech Szczerba, Rocio Costo, Sabino Veintemillas-Verdaguer, Maria Del Puerto Morales, Andreas F Thünemann
This article reports on the characterization of four superparamagnetic iron oxide nanoparticles stabilized with dimercaptosuccinic acid, which are suitable candidates for reference materials for magnetic properties. Particles p1 and p2 are single-core particles, while p3 and p4 are multi-core particles. Small-angle X-ray scattering analysis reveals a lognormal type of size distribution for the iron oxide cores of the particles. Their mean radii are 6.9 nm (p1), 10.6 nm (p2), 5.5 nm (p3) and 4.1 nm (p4), with narrow relative distribution widths of 0...
April 1, 2017: Journal of Applied Crystallography
Andrew J Allen, Fan Zhang, R Joseph Kline, William F Guthrie, Jan Ilavsky
The certification of a new standard reference material for small-angle scattering [NIST Standard Reference Material (SRM) 3600: Absolute Intensity Calibration Standard for Small-Angle X-ray Scattering (SAXS)], based on glassy carbon, is presented. Creation of this SRM relies on the intrinsic primary calibration capabilities of the ultra-small-angle X-ray scattering technique. This article describes how the intensity calibration has been achieved and validated in the certified Q range, Q = 0.008-0.25 Å(-1), together with the purpose, use and availability of the SRM...
April 1, 2017: Journal of Applied Crystallography
Barbara Eicher, Frederick A Heberle, Drew Marquardt, Gerald N Rechberger, John Katsaras, Georg Pabst
Low- and high-resolution models describing the internal transbilayer structure of asymmetric lipid vesicles have been developed. These models can be used for the joint analysis of small-angle neutron and X-ray scattering data. The models describe the underlying scattering length density/electron density profiles either in terms of slabs or through the so-called scattering density profile, previously applied to symmetric lipid vesicles. Both models yield structural details of asymmetric membranes, such as the individual area per lipid, and the hydrocarbon thickness of the inner and outer bilayer leaflets...
April 1, 2017: Journal of Applied Crystallography
S Huband, A M Glazer, K Roleder, A Majchrowski, P A Thomas
The symmetry of the intermediate high-temperature phase of PbHfO3 has been determined unambiguously to be orthorhombic using a combination of high-resolution X-ray diffraction and birefringence imaging microscopy measurements of crystal plates. While lattice parameter measurements as a function of temperature in the intermediate phase are consistent with either orthorhombic or tetragonal symmetry, domain orientations observed in birefringence imaging microscopy measurements utilizing the Metripol system are only consistent with orthorhombic symmetry with the unit cell in the rhombic orientation of the pseudocubic unit cell...
April 1, 2017: Journal of Applied Crystallography
Dominik Kriegner, Petr Harcuba, Jozef Veselý, Andreas Lesnik, Guenther Bauer, Gunther Springholz, Václav Holý
The twin distribution in topological insulators Bi2Te3 and Bi2Se3 was imaged by electron backscatter diffraction (EBSD) and scanning X-ray diffraction microscopy (SXRM). The crystal orientation at the surface, determined by EBSD, is correlated with the surface topography, which shows triangular pyramidal features with edges oriented in two different orientations rotated in the surface plane by 60°. The bulk crystal orientation is mapped out using SXRM by measuring the diffracted X-ray intensity of an asymmetric Bragg peak using a nano-focused X-ray beam scanned over the sample...
April 1, 2017: Journal of Applied Crystallography
Oier Bikondoa
Multi-time correlation functions are especially well suited to study non-equilibrium processes. In particular, two-time correlation functions are widely used in X-ray photon correlation experiments on systems out of equilibrium. One-time correlations are often extracted from two-time correlation functions at different sample ages. However, this way of analysing two-time correlation functions is not unique. Here, two methods to analyse two-time correlation functions are scrutinized, and three illustrative examples are used to discuss the implications for the evaluation of the correlation times and functional shape of the correlations...
April 1, 2017: Journal of Applied Crystallography
Dung Trung Tran, Gunnar Svensson, Cheuk-Wai Tai
SUePDF is a graphical user interface program written in MATLAB to achieve quantitative pair distribution functions (PDFs) from electron diffraction data. The program facilitates structural studies of amorphous materials and small nanoparticles using electron diffraction data from transmission electron microscopes. It is based on the physics of electron scattering as well as the total scattering methodology. A method of background modeling is introduced to treat the intensity tail of the direct beam, inelastic scattering and incoherent multiple scattering...
February 1, 2017: Journal of Applied Crystallography
Paulina Komar, Gerhard Jakob
Epitaxial multilayers and superlattice (SL) structures are gaining increasing importance as they offer the opportunity to create artificial crystals with new functionalities. These crystals deviate from the parent bulk compounds not only in terms of the lattice constants but also in the symmetry classification, which renders calculation of their X-ray diffraction (XRD) patterns tedious. Nevertheless, XRD is essential to get information on the multilayer/SL structure such as, for example, out-of-plane lattice constants, strain relaxation and period length of the crystalline SL...
February 1, 2017: Journal of Applied Crystallography
Claire A Murray, Jonathan Potter, Sarah J Day, Annabelle R Baker, Stephen P Thompson, Jon Kelly, Christopher G Morris, Sihai Yang, Chiu C Tang
A new synchrotron X-ray powder diffraction instrument has been built and commissioned for long-duration experiments on beamline I11 at Diamond Light Source. The concept is unique, with design features to house multiple experiments running in parallel, in particular with specific stages for sample environments to study slow kinetic systems or processes. The instrument benefits from a high-brightness X-ray beam and a large area detector. Diffraction data from the commissioning work have shown that the objectives and criteria are met...
February 1, 2017: Journal of Applied Crystallography
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