Journal of Applied Crystallography
http://journals.iucr.org/j/issues/2017/05/00/isscontsbdy.html
Journal of Applied Crystallography covers a wide range of crystallographic topics from the viewpoints of both techniques and theory. The journal presents articles on the application of crystallographic techniques and on the related apparatus and computer software. For many years, Journal of Applied Crystallography has been the main vehicle for the publication of small-angle scattering articles and powder diffraction techniques. The journal is the primary place where crystallographic computer program information is published.enCopyright (c) 2017 International Union of Crystallography2017-08-18International Union of CrystallographyInternational Union of Crystallographyhttp://journals.iucr.orgurn:issn:1600-5767Journal of Applied Crystallography covers a wide range of crystallographic topics from the viewpoints of both techniques and theory. The journal presents articles on the application of crystallographic techniques and on the related apparatus and computer software. For many years, Journal of Applied Crystallography has been the main vehicle for the publication of small-angle scattering articles and powder diffraction techniques. The journal is the primary place where crystallographic computer program information is published.text/htmlJournal of Applied Crystallography, Volume 50, Part 5, 2017textweekly62002-02-01T00:00+00:005502017-08-18Copyright (c) 2017 International Union of CrystallographyJournal of Applied Crystallography1245urn:issn:1600-5767med@iucr.orgAugust 20172017-08-18Journal of Applied Crystallographyhttp://journals.iucr.org/logos/rss10j.gif
http://journals.iucr.org/j/issues/2017/05/00/isscontsbdy.html
Still imageForm factor of any polyhedron: a general compact formula and its singularities
http://scripts.iucr.org/cgi-bin/paper?fs5152
A general and compact formula is established for the form factor of any polyhedron, which involves only the apex coordinates and the apex connections. For large diffusion vector q, the form factor behaves like q−3 for generic directions, but it exhibits q−2 singularities in the directions perpendicular to the edges and q−1 singularities in the directions normal to the faces. General results are established for these singularities. Using a Python implementation, illustrative examples are discussed. The generality of the formula and of its singularities are likely to be important for any discussion of scattering from polyhedral particles.Copyright (c) 2017 International Union of Crystallographyurn:issn:1600-5767Croset, B.2017-08-09doi:10.1107/S1600576717010147International Union of CrystallographyA compact and general formula for the form factor of any polyhedron is given and its singularities are discussed, together with illustrative examples.ENX-ray diffractionform factorspolyhedrananoparticlesA general and compact formula is established for the form factor of any polyhedron, which involves only the apex coordinates and the apex connections. For large diffusion vector q, the form factor behaves like q−3 for generic directions, but it exhibits q−2 singularities in the directions perpendicular to the edges and q−1 singularities in the directions normal to the faces. General results are established for these singularities. Using a Python implementation, illustrative examples are discussed. The generality of the formula and of its singularities are likely to be important for any discussion of scattering from polyhedral particles.text/htmlForm factor of any polyhedron: a general compact formula and its singularitiestext5502017-08-09Copyright (c) 2017 International Union of CrystallographyJournal of Applied Crystallographyresearch papers00Applications of dynamical theory of X-ray diffraction by perfect crystals to reciprocal space mapping
http://scripts.iucr.org/cgi-bin/paper?vh5077
The classical dynamical theory of X-ray diffraction is expanded to the special case of transversely restricted wavefronts of the incident and reflected waves. This approach allows one to simulate the two-dimensional coherently scattered intensity distribution centred around a particular reciprocal lattice vector in the so-called triple-crystal diffraction scheme. The effect of the diffractometer's instrumental function on X-ray diffraction data was studied.Copyright (c) 2017 International Union of Crystallographyurn:issn:1600-5767Punegov, V.I.Pavlov, K.M.Karpov, A.V.Faleev, N.N.2017-08-09doi:10.1107/S1600576717010123International Union of CrystallographyThe dynamical theory of X-ray diffraction has been developed for spatially restricted beams. This approach allows one to calculate rocking curves as well as reciprocal space maps for both transmitted and reflected coherent wavefields.ENX-ray dynamical diffraction theoryreciprocal space mapstransversely restricted wavefrontsinstrumental functionsThe classical dynamical theory of X-ray diffraction is expanded to the special case of transversely restricted wavefronts of the incident and reflected waves. This approach allows one to simulate the two-dimensional coherently scattered intensity distribution centred around a particular reciprocal lattice vector in the so-called triple-crystal diffraction scheme. The effect of the diffractometer's instrumental function on X-ray diffraction data was studied.text/htmlApplications of dynamical theory of X-ray diffraction by perfect crystals to reciprocal space mappingtext5502017-08-09Copyright (c) 2017 International Union of CrystallographyJournal of Applied Crystallographyresearch papers00Three-dimensional texture visualization approaches: applications to nickel and titanium alloys
http://scripts.iucr.org/cgi-bin/paper?po5097
This paper applies the three-dimensional visualization techniques explored theoretically by Callahan, Echlin, Pollock, Singh & De Graef [J. Appl. Cryst. (2017), 50, 430–440] to a series of experimentally acquired texture data sets, namely a sharp cube texture in a single-crystal Ni-based superalloy, a sharp Goss texture in single-crystal Nb, a random texture in a powder metallurgy polycrystalline René 88-DT alloy and a rolled plate texture in Ti-6Al-4V. Three-dimensional visualizations are shown (and made available as movies as supplementary material) using the Rodrigues, Euler and three-dimensional stereographic projection representations. In addition, it is shown that the true symmetry of Euler space, as derived from a mapping onto quaternion space, is described by the monoclinic color space group Pcc in the Opechowski and Guccione nomenclature.Copyright (c) 2017 International Union of Crystallographyurn:issn:1600-5767Callahan, P.G.Echlin, M.P.Stinville, J.C.Pollock, T.M.Singh, S.Ram, F.De Graef, M.2017-08-09doi:10.1107/S1600576717010470International Union of CrystallographyThis paper applies three-dimensional visualization techniques to synthetic and experimentally acquired material textures (random, cube and Goss texture components) and illustrates how three-dimensional visualization can be used to gain insight about orientation distribution functions and orientation relations. The intrinsic symmetry of the Euler orientation representations is considered in detail and it is shown that a monoclinic magnetic space group properly describes the symmetry of Euler space.ENtexture representationthree-dimensional visualizationfundamental zonesRodrigues vectorsThis paper applies the three-dimensional visualization techniques explored theoretically by Callahan, Echlin, Pollock, Singh & De Graef [J. Appl. Cryst. (2017), 50, 430–440] to a series of experimentally acquired texture data sets, namely a sharp cube texture in a single-crystal Ni-based superalloy, a sharp Goss texture in single-crystal Nb, a random texture in a powder metallurgy polycrystalline René 88-DT alloy and a rolled plate texture in Ti-6Al-4V. Three-dimensional visualizations are shown (and made available as movies as supplementary material) using the Rodrigues, Euler and three-dimensional stereographic projection representations. In addition, it is shown that the true symmetry of Euler space, as derived from a mapping onto quaternion space, is described by the monoclinic color space group Pcc in the Opechowski and Guccione nomenclature.text/htmlThree-dimensional texture visualization approaches: applications to nickel and titanium alloystext5502017-08-09Copyright (c) 2017 International Union of CrystallographyJournal of Applied Crystallographyresearch papers00Nanoparticle size distribution quantification: results of a small-angle X-ray scattering inter-laboratory comparison
http://scripts.iucr.org/cgi-bin/paper?ge5041
This paper presents the first worldwide inter-laboratory comparison of small-angle X-ray scattering (SAXS) for nanoparticle sizing. The measurands in this comparison are the mean particle radius, the width of the size distribution and the particle concentration. The investigated sample consists of dispersed silver nanoparticles, surrounded by a stabilizing polymeric shell of poly(acrylic acid). The silver cores dominate the X-ray scattering pattern, leading to the determination of their radius size distribution using (i) the generalized indirect Fourier transformation method, (ii) classical model fitting using SASfit and (iii) a Monte Carlo fitting approach using McSAS. The application of these three methods to the collected data sets from the various laboratories produces consistent mean number- and volume-weighted core radii of Rn = 2.76 (6) nm and Rv = 3.20 (4) nm, respectively. The corresponding widths of the lognormal radius distribution of the particles were σn = 0.65 (1) nm and σv = 0.71 (1) nm. The particle concentration determined using this method was 3.0 (4) g l−1 or 4.2 (7) × 10−6 mol l−1. These results are affected slightly by the choice of data evaluation procedure, but not by the instruments: the participating laboratories at synchrotron SAXS beamlines, commercial and in-house-designed instruments were all able to provide highly consistent data. This demonstrates that SAXS is a suitable method for revealing particle size distributions in the sub-20 nm region (at minimum), out of reach for most other analytical methods.Copyright (c) 2017 Brian R. Pauw et al.urn:issn:1600-5767Pauw, B.R.Kästner, C.Thünemann, A.F.2017-08-18doi:10.1107/S160057671701010XInternational Union of CrystallographyAn extensive round robin experiment between small-angle X-ray scattering laboratories has delivered a global uncertainty estimate for the measurands of a nanoparticle dispersion. Irrespective of the instrument pedigree, the distribution mean, width and volume fraction could be determined with an accuracy of 1, 10 and 10%, respectively.ENsmall-angle scatteringaccuracymethodologysilver nanoparticlespoly(acrylic acid)SASfitMcSASinverse Fourier transformround robinThis paper presents the first worldwide inter-laboratory comparison of small-angle X-ray scattering (SAXS) for nanoparticle sizing. The measurands in this comparison are the mean particle radius, the width of the size distribution and the particle concentration. The investigated sample consists of dispersed silver nanoparticles, surrounded by a stabilizing polymeric shell of poly(acrylic acid). The silver cores dominate the X-ray scattering pattern, leading to the determination of their radius size distribution using (i) the generalized indirect Fourier transformation method, (ii) classical model fitting using SASfit and (iii) a Monte Carlo fitting approach using McSAS. The application of these three methods to the collected data sets from the various laboratories produces consistent mean number- and volume-weighted core radii of Rn = 2.76 (6) nm and Rv = 3.20 (4) nm, respectively. The corresponding widths of the lognormal radius distribution of the particles were σn = 0.65 (1) nm and σv = 0.71 (1) nm. The particle concentration determined using this method was 3.0 (4) g l−1 or 4.2 (7) × 10−6 mol l−1. These results are affected slightly by the choice of data evaluation procedure, but not by the instruments: the participating laboratories at synchrotron SAXS beamlines, commercial and in-house-designed instruments were all able to provide highly consistent data. This demonstrates that SAXS is a suitable method for revealing particle size distributions in the sub-20 nm region (at minimum), out of reach for most other analytical methods.text/htmlNanoparticle size distribution quantification: results of a small-angle X-ray scattering inter-laboratory comparisontext5502017-08-18Copyright (c) 2017 Brian R. Pauw et al.Journal of Applied Crystallographyresearch papers00Determination of active layer morphology in all-polymer photovoltaic cells
http://scripts.iucr.org/cgi-bin/paper?ge5040
This study investigates the structure of films spin-coated from blends of the semiconducting polymers poly(3-hexylthiophene-2,5-diyl) (P3HT) and poly{2,6-[4,4-bis-(2-ethylhexyl)-4H-cyclopenta[2,1-b;3,4-b′]dithiophene]-alt-4,7(2,1,3-benzothiadiazole)} (PCPDTBT). Such blends are of potential use in all-polymer solar cells in which both the acceptor and the donor material generate excitons to contribute to the photocurrent. Prompted by threefold performance gains seen in polymer/fullerene and polymer blend solar cells upon addition of pristine graphene, devices are prepared from P3HT/PCPDTBT blends both with and without graphene. This report focuses on the morphology of the active layer since this is of critical importance in determining performance. Small-angle neutron scattering (SANS) is utilized to study this polymer blend with deuterated P3HT to provide contrast and permit the investigation of buried structure in neat and graphene-doped films. SANS reveals the presence of P3HT crystallites dispersed in an amorphous blend matrix of P3HT and PCPDTBT. The crystallites are approximately disc shaped and do not show any evidence of higher-order structure or aggregation. While the structure of the films does not change with the addition of graphene, there is a perceptible effect on the electronic properties and energy conversion efficiency in solar cells made from such films. Determination of the active layer morphology yields crucial insight into structure–property relationships in organic photovoltaic devices.Copyright (c) 2017 International Union of Crystallographyurn:issn:1600-5767Mulderig, A.J.Jin, Y.Yu, F.Keum, J.Hong, K.Browning, J.F.Beaucage, G.Smith, G.S.Kuppa, V.K.2017-08-18doi:10.1107/S1600576717010457International Union of CrystallographySmall-angle scattering is used to reveal the buried nanostructure and to uncover structure–property relationships in all-polymer photovoltaics.ENorganic photovoltaicssmall-angle scatteringgraphenemorphologyThis study investigates the structure of films spin-coated from blends of the semiconducting polymers poly(3-hexylthiophene-2,5-diyl) (P3HT) and poly{2,6-[4,4-bis-(2-ethylhexyl)-4H-cyclopenta[2,1-b;3,4-b′]dithiophene]-alt-4,7(2,1,3-benzothiadiazole)} (PCPDTBT). Such blends are of potential use in all-polymer solar cells in which both the acceptor and the donor material generate excitons to contribute to the photocurrent. Prompted by threefold performance gains seen in polymer/fullerene and polymer blend solar cells upon addition of pristine graphene, devices are prepared from P3HT/PCPDTBT blends both with and without graphene. This report focuses on the morphology of the active layer since this is of critical importance in determining performance. Small-angle neutron scattering (SANS) is utilized to study this polymer blend with deuterated P3HT to provide contrast and permit the investigation of buried structure in neat and graphene-doped films. SANS reveals the presence of P3HT crystallites dispersed in an amorphous blend matrix of P3HT and PCPDTBT. The crystallites are approximately disc shaped and do not show any evidence of higher-order structure or aggregation. While the structure of the films does not change with the addition of graphene, there is a perceptible effect on the electronic properties and energy conversion efficiency in solar cells made from such films. Determination of the active layer morphology yields crucial insight into structure–property relationships in organic photovoltaic devices.text/htmlDetermination of active layer morphology in all-polymer photovoltaic cellstext5502017-08-18Copyright (c) 2017 International Union of CrystallographyJournal of Applied Crystallographyresearch papers00A tool for automatic recognition of [110] tilt grain boundaries in zincblende-type crystals
http://scripts.iucr.org/cgi-bin/paper?rg5134
The local atomic structure of [110] tilt grain boundaries (GBs) formed in ∼100 nm-sized GaAs nanocrystals, which crystallize in the non-centrosymmetric zincblende-type structure with face-centred cubic lattice symmetry, was imaged and analysed by means of high-resolution high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM). The nanocrystals were grown by metal–organic vapour phase epitaxy on top of (001) Si nanotips embedded in an oxide matrix. This paper introduces an automatic analysis method and corresponding processing tool for the identification of the GBs. The method comprises (i) extraction of crystallographic parameters, i.e. misorientation angles and transformation matrices for the different crystal parts (grains/twins) observed by HAADF-STEM, and (ii) determination of their common plane(s) by modelling all possible intersections of the corresponding three-dimensional reciprocal lattices. The structural unit model is also used to characterize the GB structures and to validate the data obtained by the developed algorithm.Copyright (c) 2017 International Union of Crystallographyurn:issn:1600-5767Kozak, R.Kurdzesau, F.Prieto, I.Skibitzki, O.Schroeder, T.Arroyo Rojas Dasilva, Y.Erni, R.von Känel, H.Rossell, M.D.2017-08-18doi:10.1107/S1600576717010858International Union of CrystallographyAn automated analysis approach for recognition of grain boundaries in face-centred cubic based zincblende materials from high-resolution high-angle annular dark-field scanning transmission electron microscopy images is described and its performance is tested.ENgrain/twin boundarytransformation matricesscanning transmission electron microscopyGaAsface-centred cubic zincblende nanomaterialsThe local atomic structure of [110] tilt grain boundaries (GBs) formed in ∼100 nm-sized GaAs nanocrystals, which crystallize in the non-centrosymmetric zincblende-type structure with face-centred cubic lattice symmetry, was imaged and analysed by means of high-resolution high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM). The nanocrystals were grown by metal–organic vapour phase epitaxy on top of (001) Si nanotips embedded in an oxide matrix. This paper introduces an automatic analysis method and corresponding processing tool for the identification of the GBs. The method comprises (i) extraction of crystallographic parameters, i.e. misorientation angles and transformation matrices for the different crystal parts (grains/twins) observed by HAADF-STEM, and (ii) determination of their common plane(s) by modelling all possible intersections of the corresponding three-dimensional reciprocal lattices. The structural unit model is also used to characterize the GB structures and to validate the data obtained by the developed algorithm.text/htmlA tool for automatic recognition of [110] tilt grain boundaries in zincblende-type crystalstext5502017-08-18Copyright (c) 2017 International Union of CrystallographyJournal of Applied Crystallographyresearch papers00Direction indices for crystal lattices
http://scripts.iucr.org/cgi-bin/paper?gj5187
Direction indices [uvw] of rational directions in crystal lattices are commonly restricted to integer numbers. This restriction is correct only when primitive unit cells are used. In the case of centred cells, however, direction indices may take fractional values too, because the first lattice node after the origin along a direction can have fractional coordinates in a centred basis. This evidence is very often overlooked and an undue simplification of direction indices to integer values is usually adopted. Although such a simplification does not affect the identification of the direction, it is potentially a source of confusion and mistakes in crystallographic calculations. A parallel is made with the incorrect restriction of Miller indices to relatively prime integers in centred cells.Copyright (c) 2017 International Union of Crystallographyurn:issn:1600-5767Nespolo, M.2017-08-09doi:10.1107/S1600576717010548International Union of CrystallographyThe incorrect restriction to integer values for direction indices in centred cells and the potential consequences are pointed out and corrected.ENdirection indicesMiller indicescentred cellsDirection indices [uvw] of rational directions in crystal lattices are commonly restricted to integer numbers. This restriction is correct only when primitive unit cells are used. In the case of centred cells, however, direction indices may take fractional values too, because the first lattice node after the origin along a direction can have fractional coordinates in a centred basis. This evidence is very often overlooked and an undue simplification of direction indices to integer values is usually adopted. Although such a simplification does not affect the identification of the direction, it is potentially a source of confusion and mistakes in crystallographic calculations. A parallel is made with the incorrect restriction of Miller indices to relatively prime integers in centred cells.text/htmlDirection indices for crystal latticestext5502017-08-09Copyright (c) 2017 International Union of CrystallographyJournal of Applied Crystallographyteaching and education00A simple device for transferring an oriented crystal from an X-ray Laue diffractometer to a cutting machine
http://scripts.iucr.org/cgi-bin/paper?vg5073
A simple transfer device is described that enables cutting of an oriented single crystal.Copyright (c) 2017 International Union of Crystallographyurn:issn:1600-5767Stishov, S.M.2017-08-18doi:10.1107/S1600576717010469International Union of CrystallographyA simple transfer device is described that enables cutting of an oriented single crystal.ENcrystal orientationLaue X-ray diffractionA simple transfer device is described that enables cutting of an oriented single crystal.text/htmlA simple device for transferring an oriented crystal from an X-ray Laue diffractometer to a cutting machinetext5502017-08-18Copyright (c) 2017 International Union of CrystallographyJournal of Applied Crystallographylaboratory notes00