issue contents

Journal logoJOURNAL OF
APPLIED
CRYSTALLOGRAPHY
ISSN: 1600-5767

December 2017 issue

Highlighted illustration

Cover illustration: Images from The electrostatic potential of dynamic charge densities [Hübschle & van Smaalen (2017). J. Appl. Cryst. 50, 1627-1636].

research papers


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The computing speed of reverse Monte Carlo structure refinements has been improved by up to two orders of magnitude, which significantly expands the capabilities of this method.

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A method for generating high-quality discretizations of SO(3) is described and compared with existing methods.

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The first direct valence-selective structure determination by X-ray fluorescence holography is presented. This method uses the fluorescence intensity variation of specific elements close to the K absorption edge. Thereby, the different crystal structures in a mixed Y2+/Y3+ thin film of yttrium oxide are distinguished.

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The size dependences of the melting and crystallization temperatures of spherical Bi nanoparticles embedded in glass were determined using combined small- and wide-angle X-ray scattering measurements for nanoparticle radii ranging from 1 to 11 nm. The results provide additional and stronger evidence supporting previous conclusions showing that, below the melting temperature, Bi nanocrystals with radii larger than 1.8 nm consist of a crystalline core surrounded by a disordered shell.

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Pulsed neutron Bragg-dip transmission is an efficient method for determining the crystallographic direction of crystals lying parallel to the incident beam. The method can be used for crystalline grain identification with a spatial resolution higher than that achievable by neutron diffraction imaging.

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Reverse Monte Carlo software to analyze the atomic arrangements of perovskite oxide ultrathin films from the crystal truncation rod intensity is developed on the basis of Bayesian inference.

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A single-particle structural model of schwertmannite is proposed from a combined multi-technique approach, using a novel reverse Monte Carlo/Debye scattering equation parallel code.

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The electrostatic potential (ESP) is computed for dynamic charge densities corresponding to multipole models and maximum-entropy densities. Convergence of the reciprocal-space summation is guaranteed by the Gaussian form of the Debye–Waller factor. Applications to serine demonstrate only a weak temperature dependence of the ESP on molecular surfaces relevant to intermolecular interactions.

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Phase-retrieval algorithms combined with global optimization techniques have been shown to be robust and reliable, and to outperform phase-retrieval algorithms used in coherent diffractive imaging.

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Variant selection is reported in martensite formed on the surface of an Fe–30% Ni sample. Predictive models of the phenomenon based on different crystallographic descriptions of the transformation are proposed and compared.

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Generalized skew-symmetric interfacial probability density functions are used to model arbitrary interfacial density profiles for the analysis of reflectivity and small-angle scattering.

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Two algorithms reliant on physics-based forward models are proposed to refine crystal orientations: a multi-resolution brute-force local search and a derivative-free optimization. The efficacy of these methods is evaluated for the electron backscatter diffraction and electron channeling pattern modalities using simulated patterns with known orientations.

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A modeling framework to relate the molecular orientation of nanostructures to polarized resonant soft X-ray scattering measurements using the Born approximation and a full tensor treatment is described.

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This study presents rhombohedral twin characterization in plastically deformed alumina at high-pressure and -temperature conditions using electron channeling contrast imaging (ECCI) in a field emission scanning electron microscope, electron backscatter diffraction (EBSD) and elastic plastic self-consistent (EPSC) numerical modeling on synchrotron X-ray diffraction data.

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This manuscript addresses the problem of peak finding and, by extension, `hit finding' in crystallographic X-ray free-electron laser datasets, by exploiting recent developments in robust statistical analysis.

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In this article, the effect of phenol red dye on key structural, crystalline perfection, optical, photoluminescence and dielectric properties of zinc (tris) thio­urea sulfate single crystals is reported.

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Compositional fluctuations arising from Cu-rich solute clusters in Al–Cu alloys with additions of Li and Mg are characterized by combined small-angle neutron and X-ray scattering.

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This article presents a stress tensor spherical harmonics expansion with the Reuss ground state, which is used for macro strain/stress investigation by powder diffraction.

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A method and software tool are introduced to fit a series of pair distribution function data through a phase transition or to detect and track a specific structural feature of interest using a linear combination of two end-member states. The misfit between the model combination and the data can reveal underlying details regarding the nature and length scale of intermediate structures.

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Laue microdiffraction coupled with energy measurements is used to determine the full elastic strain tensor related to the γ and γ′ phases in a coarse-grained nickel-based superalloy. Model microstructures with a 200 or 2000 nm average precipitate size are investigated.

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The impact of the edge roughness of laterally periodic nanostructures on the scattering pattern is investigated. The applicability of existing analytical approaches for the description of real samples is discussed.

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This paper describes a proof-of-principle study demonstrating that protein crystals ablated by a picosecond infrared laser retain their diffractive properties. The crystals were ejected at high speed from an aqueous solution, collected and then used for structure determination by serial synchrotron crystallography.

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The lattice thermal expansion of Pu1−yAmyO2−x mixed oxides was studied in situ in reconstituted air by high-temperature X-ray diffraction. The lattice parameter of the face-centred cubic phase constituting the materials studied exhibited a more pronounced deviation from linearity as a function of both temperature and americium content in the mixed oxides.

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The thermal diffuse scattering (TDS) contribution to the integrated Bragg intensities is calculated and quantified, and the implications of uncorrected TDS for crystallographic models investigated.

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A data correction sequence is presented, consisting of ordered elementary steps that extract the small-angle X-ray scattering cross section from the original detector signal(s). It is applicable to a wide range of samples, including solids and dispersions.

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The Shift_and_Fix procedure is a new, automatic computational process which has been developed and introduced in the EXPO package for optimizing a structure model and increasing the probability of succeeding in the ab initio powder solution by direct methods.

computer programs


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NanoPDF64 is a software package for analysis of pair distribution functions of nanocrystals. It is also capable of calculating theoretical powder diffraction patterns and pair distribution functions for atomistic models of nanocrystals.

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CarbonXS GUI is a graphical user interface to CarbonXS. It is used to fit the X-ray diffraction patterns of disordered and graphitized carbon materials to extract structural parameters such as coherence size and strain.

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A relatively simple method for users new to modulated structures to implement such structural features in an atomistic Monte Carlo modelling program (ZMC) is described. The relevance and usefulness of such a method are outlined.

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The ccCluster program provides an easy-to-use interface to perform hierarchical cluster analysis on protein diffraction datasets.

addenda and errata


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