Forthcoming article in Acta Crystallographica Section A Foundations and Advances
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Acta Crystallographica Section A: Foundations and Advances covers theoretical and fundamental aspects of the structure of matter. The journal is the prime forum for research in diffraction physics and the theory of crystallographic structure determination by diffraction methods using X-rays, neutrons and electrons. The structures include periodic and aperiodic crystals, and non-periodic disordered materials, and the corresponding Bragg, satellite and diffuse scattering, thermal motion and symmetry aspects. Spatial resolutions range from the subatomic domain in charge-density studies to nanodimensional imperfections such as dislocations and twin walls. The chemistry encompasses metals, alloys, and inorganic, organic and biological materials. Structure prediction and properties such as the theory of phase transformations are also covered.en-gbCopyright (c) 2015 International Union of CrystallographyInternational Union of CrystallographyInternational Union of Crystallographyhttp://journals.iucr.orgurn:issn:0108-7673Acta Crystallographica Section A: Foundations and Advances covers theoretical and fundamental aspects of the structure of matter. The journal is the prime forum for research in diffraction physics and the theory of crystallographic structure determination by diffraction methods using X-rays, neutrons and electrons. The structures include periodic and aperiodic crystals, and non-periodic disordered materials, and the corresponding Bragg, satellite and diffuse scattering, thermal motion and symmetry aspects. Spatial resolutions range from the subatomic domain in charge-density studies to nanodimensional imperfections such as dislocations and twin walls. The chemistry encompasses metals, alloys, and inorganic, organic and biological materials. Structure prediction and properties such as the theory of phase transformations are also covered.text/htmlActa Crystallographica Section A Foundations and Advancestextdaily12002-01-01T00:00+00:00med@iucr.orgActa Crystallographica Section A Foundations and AdvancesCopyright (c) 2015 International Union of Crystallographyurn:issn:0108-7673Forthcoming article in Acta Crystallographica Section A Foundations and Advanceshttp://journals.iucr.org/logos/rss10a.gif
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Still imageDistribution rules of systematic absences on the Conway topograph and their application to powder auto-indexing: erratum
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Copyright (c) 2015 International Union of Crystallographyurn:issn:2053-2733O-Tomiyasudoi:International Union of Crystallographyentext/htmlDistribution rules of systematic absences on the Conway topograph and their application to powder auto-indexing: erratumtextPeriodic entanglement III: tangled degree-three finite and layer net inter-growths from rare forests
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Entanglements of three-periodic arrays of θ-graphs and regular two-dimensional honeycomb (hcb) nets are constructed from free tilings of the hyperbolic plane consisting of rare packings of regular trees mapped onto the P, D, G and H triply periodic minimal surfaces.Copyright (c) 2015 International Union of Crystallographyurn:issn:2053-2733Evans and Hydedoi:International Union of CrystallographyEntanglements of three-periodic arrays of θ-graphs and regular two-dimensional honeycomb (hcb) nets are constructed from free tilings of the hyperbolic plane consisting of rare packings of regular trees mapped onto the P, D, G and H triply periodic minimal surfaces.enEntanglements of three-periodic arrays of θ-graphs and regular two-dimensional honeycomb (hcb) nets are constructed from free tilings of the hyperbolic plane consisting of rare packings of regular trees mapped onto the P, D, G and H triply periodic minimal surfaces.text/htmlPeriodic entanglement III: tangled degree-three finite and layer net inter-growths from rare foreststextSolution of the phase problem at non-atomic resolution by the phantom derivative method
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The method of multiple phantom derivatives allows one to solve ab initio and at non-atomic resolution the crystallographic phase problem for a target structure by using random structures with the same unit cell and space-group symmetry: the composite structures, called derivatives, are devoid of experimental data. The method is also suitable for extending and refining phases obtained by other techniques.Copyright (c) 2015 International Union of Crystallographyurn:issn:2053-2733Carmelo Giacovazzodoi:10.1107/S2053273315013856International Union of CrystallographyThe method of multiple phantom derivatives allows one to solve ab initio and at non-atomic resolution the crystallographic phase problem for a target structure by using random structures with the same unit cell and space-group symmetry: the composite structures, called derivatives, are devoid of experimental data. The method is also suitable for extending and refining phases obtained by other techniques.enAB INITIO SOLUTION; PHASING METHODS; DERIVATIVE STRUCTUREThe method of multiple phantom derivatives allows one to solve ab initio and at non-atomic resolution the crystallographic phase problem for a target structure by using random structures with the same unit cell and space-group symmetry: the composite structures, called derivatives, are devoid of experimental data. The method is also suitable for extending and refining phases obtained by other techniques.text/htmlSolution of the phase problem at non-atomic resolution by the phantom derivative methodtextHexagonal projected symmetries
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A list of the three-dimensional lattices that can be projected so as to obtain a two-dimensional hexagonal pattern is established.Copyright (c) 2015 International Union of Crystallographyurn:issn:2053-2733Juliane F. Oliveira et al.doi:10.1107/S2053273315012905International Union of CrystallographyA list of the three-dimensional lattices that can be projected so as to obtain a two-dimensional hexagonal pattern is established.enSYMMETRIC PATTERNS; PROJECTED PATTERNS; HEXAGONAL SYMMETRIESA list of the three-dimensional lattices that can be projected so as to obtain a two-dimensional hexagonal pattern is established.text/htmlHexagonal projected symmetriestextThree new crystal structures in the Na–Pb system: solving structures without additional experimental input
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Three compounds in the Na–Pb binary system are solved using the First-Principles Assisted Structure Solution method.Copyright (c) 2015 International Union of Crystallographyurn:issn:2053-2733Logan Ward et al.doi:10.1107/S2053273315012516International Union of CrystallographyThree compounds in the Na–Pb binary system are solved using the First-Principles Assisted Structure Solution method.enNA-PB BINARY; STRUCTURE SOLUTION; FPASSThree compounds in the Na–Pb binary system are solved using the First-Principles Assisted Structure Solution method.text/htmlThree new crystal structures in the Na–Pb system: solving structures without additional experimental inputtextImage definition evaluation functions for X-ray crystallography: a new perspective on the phase problem
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The phase problem of X-ray crystallography is surveyed from a perspective of image definition evaluation functions. The reconstructed electron-density maps are taken as the images of the real electron distribution in crystals, and two image definition evaluation functions are proposed to identify the correct phase set.Copyright (c) 2015 International Union of Crystallographyurn:issn:2053-2733Li, He and Zhangdoi:10.1107/S2053273315012103International Union of CrystallographyThe phase problem of X-ray crystallography is surveyed from a perspective of image definition evaluation functions. The reconstructed electron-density maps are taken as the images of the real electron distribution in crystals, and two image definition evaluation functions are proposed to identify the correct phase set.enPHASE PROBLEM; IMAGE DEFINITION EVALUATION FUNCTIONS; POWER SPECTRUM ENTROPY; ITERATION ALGORITHMS; CHARGE-DENSITY MAPSThe phase problem of X-ray crystallography is surveyed from a perspective of image definition evaluation functions. The reconstructed electron-density maps are taken as the images of the real electron distribution in crystals, and two image definition evaluation functions are proposed to identify the correct phase set.text/htmlImage definition evaluation functions for X-ray crystallography: a new perspective on the phase problemtextA study of X-ray multiple diffraction by means of section topography
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The theoretical and experimental study of two different cases of X-ray multiple diffraction by means of section topography for 400 diffraction in a silicon single crystal is described. Accurate computer simulations of the section topogram for the case of X-ray multiple diffraction are performed for the first time. The experiment is carried out using a laboratory source under conditions of low resolution over the azimuthal angle.Copyright (c) 2015 International Union of Crystallographyurn:issn:2053-2733Kohn and Smirnovadoi:10.1107/S2053273315012176International Union of CrystallographyThe theoretical and experimental study of two different cases of X-ray multiple diffraction by means of section topography for 400 diffraction in a silicon single crystal is described. Accurate computer simulations of the section topogram for the case of X-ray multiple diffraction are performed for the first time. The experiment is carried out using a laboratory source under conditions of low resolution over the azimuthal angle.enX-RAY DIFFRACTION; SECTION TOPOGRAPHY; MULTIPLE DIFFRACTION; COMPUTER SIMULATIONS; LABORATORY STUDYThe theoretical and experimental study of two different cases of X-ray multiple diffraction by means of section topography for 400 diffraction in a silicon single crystal is described. Accurate computer simulations of the section topogram for the case of X-ray multiple diffraction are performed for the first time. The experiment is carried out using a laboratory source under conditions of low resolution over the azimuthal angle.text/htmlA study of X-ray multiple diffraction by means of section topographytextNeutron interferometric measurement and calculations of a phase shift induced by Laue transmission
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In this study, the phase shift induced by Laue transmission in a perfect Si crystal blade is investigated. This `Laue phase', with a fascinating steep slope, was measured in the vicinity of the Bragg condition within a neutron interferometer.Copyright (c) 2015 International Union of Crystallographyurn:issn:2053-2733T. Potocar et al.doi:10.1107/S205327331501205XInternational Union of CrystallographyIn this study, the phase shift induced by Laue transmission in a perfect Si crystal blade is investigated. This `Laue phase', with a fascinating steep slope, was measured in the vicinity of the Bragg condition within a neutron interferometer.enNEUTRON INTERFEROMETRY; PERFECT CRYSTAL INTERFEROMETER; LARGE-AREA INTERFEROMETER; DYNAMICAL DIFFRACTION; BEAM DEFLECTION; NEUTRON-ELECTRON SCATTERING LENGTHSIn this study, the phase shift induced by Laue transmission in a perfect Si crystal blade is investigated. This `Laue phase', with a fascinating steep slope, was measured in the vicinity of the Bragg condition within a neutron interferometer.text/htmlNeutron interferometric measurement and calculations of a phase shift induced by Laue transmissiontextInterpretation of angular symmetries in electron nanodiffraction patterns from thin amorphous specimens
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The interpretation of angular symmetries in electron nanodiffraction patterns from thin amorphous specimens is discussed. It is demonstrated that dynamical scattering decreases the angular symmetry of the diffraction pattern from that obtained in the kinematical approximation, and that this effect dominates over other experimental parameters such as probe-forming lens aberrations and camera noise. The decrease in angular symmetry of the diffraction pattern is demonstrated using the phase grating and multislice formalisms. A method is demonstrated whereby the dynamical data can be corrected to recover the kinematical result.Copyright (c) 2015 International Union of Crystallographyurn:issn:2053-2733Amelia C. Y. Liu et al.doi:10.1107/S2053273315011845International Union of CrystallographyThe interpretation of angular symmetries in electron nanodiffraction patterns from thin amorphous specimens is discussed. It is demonstrated that dynamical scattering decreases the angular symmetry of the diffraction pattern from that obtained in the kinematical approximation, and that this effect dominates over other experimental parameters such as probe-forming lens aberrations and camera noise. The decrease in angular symmetry of the diffraction pattern is demonstrated using the phase grating and multislice formalisms. A method is demonstrated whereby the dynamical data can be corrected to recover the kinematical result.enAMORPHOUS MATERIALS; ELECTRON NANODIFFRACTION; SHORT-RANGE ORDER; SCANNING TRANSMISSION ELECTON MICROSCOPY; FRIEDEL SYMMETRYThe interpretation of angular symmetries in electron nanodiffraction patterns from thin amorphous specimens is discussed. It is demonstrated that dynamical scattering decreases the angular symmetry of the diffraction pattern from that obtained in the kinematical approximation, and that this effect dominates over other experimental parameters such as probe-forming lens aberrations and camera noise. The decrease in angular symmetry of the diffraction pattern is demonstrated using the phase grating and multislice formalisms. A method is demonstrated whereby the dynamical data can be corrected to recover the kinematical result.text/htmlInterpretation of angular symmetries in electron nanodiffraction patterns from thin amorphous specimenstextTheoretical analysis of reflection high-energy electron diffraction (RHEED) and reflection high-energy positron diffraction (RHEPD) intensity oscillations expected for the perfect layer-by-layer growth
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The importance of the phenomenon of the refraction of waves in the behaviour of the phase shift of intensity oscillations for RHEED and RHEPD is discussed using a simple model of the interference of two waves along with the precise dynamical diffraction theory.Copyright (c) 2015 International Union of Crystallographyurn:issn:2053-2733Zbigniew Mituradoi:10.1107/S2053273315010608International Union of CrystallographyThe importance of the phenomenon of the refraction of waves in the behaviour of the phase shift of intensity oscillations for RHEED and RHEPD is discussed using a simple model of the interference of two waves along with the precise dynamical diffraction theory.enRHEED; RHEPD; DYNAMICAL DIFFRACTION THEORY; NANOLAYERSThe importance of the phenomenon of the refraction of waves in the behaviour of the phase shift of intensity oscillations for RHEED and RHEPD is discussed using a simple model of the interference of two waves along with the precise dynamical diffraction theory.text/htmlTheoretical analysis of reflection high-energy electron diffraction (RHEED) and reflection high-energy positron diffraction (RHEPD) intensity oscillations expected for the perfect layer-by-layer growthtext