Acta Crystallographica Section A
http://journals.iucr.org/a/issues/2016/02/00/isscontsbdy.html
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.enCopyright (c) 2016 International Union of Crystallography2016-02-05International Union of CrystallographyInternational Union of Crystallographyhttp://journals.iucr.orgurn:issn:2053-2733Acta 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 Advances, Volume 72, Part 2, 2016textweekly62002-01-01T00:00+00:002722016-02-05Copyright (c) 2016 International Union of CrystallographyActa Crystallographica Section A: Foundations and Advances177urn:issn:2053-2733med@iucr.orgFebruary 20162016-02-05Acta Crystallographica Section Ahttp://journals.iucr.org/logos/rss10a.gif
http://journals.iucr.org/a/issues/2016/02/00/isscontsbdy.html
Still imageCryogenic coherent X-ray diffraction imaging of biological samples at SACLA: a correlative approach with cryo-electron and light microscopy
http://scripts.iucr.org/cgi-bin/paper?mq5039
Coherent X-ray diffraction imaging at cryogenic temperature (cryo-CXDI) allows the analysis of internal structures of unstained, non-crystalline, whole biological samples in micrometre to sub-micrometre dimensions. Targets include cells and cell organelles. This approach involves preparing frozen-hydrated samples under controlled humidity, transferring the samples to a cryo-stage inside a vacuum chamber of a diffractometer, and then exposing the samples to coherent X-rays. Since 2012, cryo-coherent diffraction imaging (CDI) experiments have been carried out with the X-ray free-electron laser (XFEL) at the SPring-8 Ångstrom Compact free-electron LAser (SACLA) facility in Japan. Complementary use of cryo-electron microscopy and/or light microscopy is highly beneficial for both pre-checking samples and studying the integrity or nature of the sample. This article reports the authors' experience in cryo-XFEL-CDI of biological cells and organelles at SACLA, and describes an attempt towards reliable and higher-resolution reconstructions, including signal enhancement with strong scatterers and Patterson-search phasing.Copyright (c) 2016 International Union of Crystallographyurn:issn:2053-2733Takayama, Y.Yonekura, K.2016-01-29doi:10.1107/S2053273315023980International Union of CrystallographyCryogenic coherent X-ray diffraction imaging can be used for structural analysis of unstained, non-crystalline, whole biological samples such as cells and cell organelles. This article reports on current and future applications of cryo-coherent diffraction imaging with the X-ray free-electron laser (XFEL) at the Japanese XFEL facility, SACLA, and demonstrates the merit of a correlative approach with cryo-electron and light microscopy.ENcoherent X-ray diffraction imagingX-ray free-electron lasersfrozen-hydrated non-crystalline samplesstructural analysiscorrelative microscopyCoherent X-ray diffraction imaging at cryogenic temperature (cryo-CXDI) allows the analysis of internal structures of unstained, non-crystalline, whole biological samples in micrometre to sub-micrometre dimensions. Targets include cells and cell organelles. This approach involves preparing frozen-hydrated samples under controlled humidity, transferring the samples to a cryo-stage inside a vacuum chamber of a diffractometer, and then exposing the samples to coherent X-rays. Since 2012, cryo-coherent diffraction imaging (CDI) experiments have been carried out with the X-ray free-electron laser (XFEL) at the SPring-8 Ångstrom Compact free-electron LAser (SACLA) facility in Japan. Complementary use of cryo-electron microscopy and/or light microscopy is highly beneficial for both pre-checking samples and studying the integrity or nature of the sample. This article reports the authors' experience in cryo-XFEL-CDI of biological cells and organelles at SACLA, and describes an attempt towards reliable and higher-resolution reconstructions, including signal enhancement with strong scatterers and Patterson-search phasing.text/htmlCryogenic coherent X-ray diffraction imaging of biological samples at SACLA: a correlative approach with cryo-electron and light microscopytext2722016-01-29Copyright (c) 2016 International Union of CrystallographyActa Crystallographica Section Afeature articles00Bragg–von Laue diffraction generalized to twisted X-rays
http://scripts.iucr.org/cgi-bin/paper?vk5008
A pervasive limitation of nearly all practical X-ray methods for the determination of the atomic scale structure of matter is the need to crystallize the molecule, compound or alloy in a sufficiently large (∼10 × 10 × 10 µm) periodic array. In this paper an X-ray method applicable to structure determination of some important noncrystalline structures is proposed. It is designed according to a strict mathematical analog of von Laue's method, but replacing the translation group by another symmetry group, and simultaneously replacing plane waves by different exact closed-form solutions of Maxwell's equations. Details are presented for helical structures like carbon nanotubes or filamentous viruses. In computer simulations the accuracy of the determination of structure is shown to be comparable to the periodic case.Copyright (c) 2016 International Union of Crystallographyurn:issn:2053-2733Jüstel, D.Friesecke, G.James, R.D.2016-01-29doi:10.1107/S2053273315024390International Union of CrystallographyAn X-ray method of structure determination for some important noncrystalline structures is proposed.ENX-ray diffractionstructure determinationnoncrystalline structurestwisted X-raysA pervasive limitation of nearly all practical X-ray methods for the determination of the atomic scale structure of matter is the need to crystallize the molecule, compound or alloy in a sufficiently large (∼10 × 10 × 10 µm) periodic array. In this paper an X-ray method applicable to structure determination of some important noncrystalline structures is proposed. It is designed according to a strict mathematical analog of von Laue's method, but replacing the translation group by another symmetry group, and simultaneously replacing plane waves by different exact closed-form solutions of Maxwell's equations. Details are presented for helical structures like carbon nanotubes or filamentous viruses. In computer simulations the accuracy of the determination of structure is shown to be comparable to the periodic case.text/htmlBragg–von Laue diffraction generalized to twisted X-raystext2722016-01-29Copyright (c) 2016 International Union of CrystallographyActa Crystallographica Section Aresearch papers00Three-dimensional propagation in near-field tomographic X-ray phase retrieval
http://scripts.iucr.org/cgi-bin/paper?mq5036
This paper presents an extension of phase retrieval algorithms for near-field X-ray (propagation) imaging to three dimensions, enhancing the quality of the reconstruction by exploiting previously unused three-dimensional consistency constraints. The approach is based on a novel three-dimensional propagator and is derived for the case of optically weak objects. It can be easily implemented in current phase retrieval architectures, is computationally efficient and reduces the need for restrictive prior assumptions, resulting in superior reconstruction quality.Copyright (c) 2016 Ruhlandt and Salditturn:issn:2053-2733Ruhlandt, A.Salditt, T.2016-01-29doi:10.1107/S2053273315022469International Union of CrystallographyAn extension of phase retrieval algorithms for near-field X-ray (propagation) imaging to three dimensions is presented, enhancing the quality of the reconstruction by exploiting previously unused three-dimensional consistency constraints.ENtomographyphase retrievalX-ray imagingThis paper presents an extension of phase retrieval algorithms for near-field X-ray (propagation) imaging to three dimensions, enhancing the quality of the reconstruction by exploiting previously unused three-dimensional consistency constraints. The approach is based on a novel three-dimensional propagator and is derived for the case of optically weak objects. It can be easily implemented in current phase retrieval architectures, is computationally efficient and reduces the need for restrictive prior assumptions, resulting in superior reconstruction quality.text/htmlThree-dimensional propagation in near-field tomographic X-ray phase retrievaltext2722016-01-29Copyright (c) 2016 Ruhlandt and SaldittActa Crystallographica Section Aresearch papers00Anion order in perovskites: a group-theoretical analysis
http://scripts.iucr.org/cgi-bin/paper?kx5046
Anion ordering in the structure of cubic perovskite has been investigated by the group-theoretical method. The possibility of the existence of 261 ordered low-symmetry structures, each with a unique space-group symmetry, is established. These results include five binary and 14 ternary anion superstructures. The 261 idealized anion-ordered perovskite structures are considered as aristotypes, giving rise to different derivatives. The structures of these derivatives are formed by tilting of BO6 octahedra, distortions caused by the cooperative Jahn–Teller effect and other physical effects. Some derivatives of aristotypes exist as real substances, and some as virtual ones. A classification of aristotypes of anion superstructures in perovskite is proposed: the AX class (the simultaneous ordering of A cations and anions in cubic perovskite structure), the BX class (the simultaneous ordering of B cations and anions) and the X class (the ordering of anions only in cubic perovskite structure). In most perovskites anion ordering is accompanied by cation ordering. Therefore, the main classes of anion order in perovskites are the AX and BX classes. The calculated structures of some anion superstructures are reported. Comparison of predictions and experimentally investigated anion superstructures shows coherency of theoretical and experimental results.Copyright (c) 2016 International Union of Crystallographyurn:issn:2053-2733Talanov, M.V.Shirokov, V.B.Talanov, V.M.2016-01-29doi:10.1107/S2053273315022147International Union of CrystallographyAll aristotypes of anion superstructures in the perovskite family of crystals are established. The calculated structures of some anion superstructures are reported.ENgroup-theoretical analysisanion orderperovskitesaristotypessuperstructuresoxygen vacancy orderingAnion ordering in the structure of cubic perovskite has been investigated by the group-theoretical method. The possibility of the existence of 261 ordered low-symmetry structures, each with a unique space-group symmetry, is established. These results include five binary and 14 ternary anion superstructures. The 261 idealized anion-ordered perovskite structures are considered as aristotypes, giving rise to different derivatives. The structures of these derivatives are formed by tilting of BO6 octahedra, distortions caused by the cooperative Jahn–Teller effect and other physical effects. Some derivatives of aristotypes exist as real substances, and some as virtual ones. A classification of aristotypes of anion superstructures in perovskite is proposed: the AX class (the simultaneous ordering of A cations and anions in cubic perovskite structure), the BX class (the simultaneous ordering of B cations and anions) and the X class (the ordering of anions only in cubic perovskite structure). In most perovskites anion ordering is accompanied by cation ordering. Therefore, the main classes of anion order in perovskites are the AX and BX classes. The calculated structures of some anion superstructures are reported. Comparison of predictions and experimentally investigated anion superstructures shows coherency of theoretical and experimental results.text/htmlAnion order in perovskites: a group-theoretical analysistext2722016-01-29Copyright (c) 2016 International Union of CrystallographyActa Crystallographica Section Aresearch papers00Ab initio structure determination of nanocrystals of organic pharmaceutical compounds by electron diffraction at room temperature using a Timepix quantum area direct electron detector
http://scripts.iucr.org/cgi-bin/paper?td5026
Until recently, structure determination by transmission electron microscopy of beam-sensitive three-dimensional nanocrystals required electron diffraction tomography data collection at liquid-nitrogen temperature, in order to reduce radiation damage. Here it is shown that the novel Timepix detector combines a high dynamic range with a very high signal-to-noise ratio and single-electron sensitivity, enabling ab initio phasing of beam-sensitive organic compounds. Low-dose electron diffraction data (∼0.013 e− Å−2 s−1) were collected at room temperature with the rotation method. It was ascertained that the data were of sufficient quality for structure solution using direct methods using software developed for X-ray crystallography (XDS, SHELX) and for electron crystallography (ADT3D/PETS, SIR2014).Copyright (c) 2016 E. van Genderen et al.urn:issn:2053-2733van Genderen, E.Clabbers, M.T.B.Das, P.P.Stewart, A.Nederlof, I.Barentsen, K.C.Portillo, Q.Pannu, N.S.Nicolopoulos, S.Gruene, T.Abrahams, J.P.2016-02-05doi:10.1107/S2053273315022500International Union of CrystallographyA specialized quantum area detector for electron diffraction studies makes it possible to solve the structure of small organic compound nanocrystals in non-cryo conditions by direct methods.ENelectron nanocrystallographyTimepix quantum area detectorcarbamazepinenicotinic acidelectron diffraction structure determinationUntil recently, structure determination by transmission electron microscopy of beam-sensitive three-dimensional nanocrystals required electron diffraction tomography data collection at liquid-nitrogen temperature, in order to reduce radiation damage. Here it is shown that the novel Timepix detector combines a high dynamic range with a very high signal-to-noise ratio and single-electron sensitivity, enabling ab initio phasing of beam-sensitive organic compounds. Low-dose electron diffraction data (∼0.013 e− Å−2 s−1) were collected at room temperature with the rotation method. It was ascertained that the data were of sufficient quality for structure solution using direct methods using software developed for X-ray crystallography (XDS, SHELX) and for electron crystallography (ADT3D/PETS, SIR2014).text/htmlAb initio structure determination of nanocrystals of organic pharmaceutical compounds by electron diffraction at room temperature using a Timepix quantum area direct electron detectortext2722016-02-05Copyright (c) 2016 E. van Genderen et al.Acta Crystallographica Section Aresearch papers0014388021438803143880414388051438806Wiener index on rows of unit cells of the face-centred cubic lattice
http://scripts.iucr.org/cgi-bin/paper?eo5052
The Wiener index of a connected graph, known as the `sum of distances', is the first topological index used in chemistry to sum the distances between all unordered pairs of vertices of a graph. The Wiener index, sometimes called the Wiener number, is one of the indices associated with a molecular graph that correlates physical and chemical properties of the molecule, and has been studied for various kinds of graphs. In this paper, the graphs of lines of unit cells of the face-centred cubic lattice are investigated. This lattice is one of the simplest, the most symmetric and the most usual, cubic crystal lattices. Its graphs contain face centres of the unit cells and other vertices, called cube vertices. Closed formulae are obtained to calculate the sum of shortest distances between pairs of cube vertices, between cube vertices and face centres and between pairs of face centres. Based on these formulae, their sum, the Wiener index of a face-centred cubic lattice with unit cells connected in a row graph, is computed.Copyright (c) 2016 International Union of Crystallographyurn:issn:2053-2733Mujahed, H.Nagy, B.2016-02-05doi:10.1107/S2053273315022743International Union of CrystallographyThe Wiener index of various graphs represents a structure compactness measure of the graph. The face-centred cubic lattice is one of the most usual crystal lattices; in this paper, the Wiener index of its graph is computed having unit cells in a row.ENWiener indexface-centred cubic latticeshortest pathsnon-traditional gridscombinatorics on gridsThe Wiener index of a connected graph, known as the `sum of distances', is the first topological index used in chemistry to sum the distances between all unordered pairs of vertices of a graph. The Wiener index, sometimes called the Wiener number, is one of the indices associated with a molecular graph that correlates physical and chemical properties of the molecule, and has been studied for various kinds of graphs. In this paper, the graphs of lines of unit cells of the face-centred cubic lattice are investigated. This lattice is one of the simplest, the most symmetric and the most usual, cubic crystal lattices. Its graphs contain face centres of the unit cells and other vertices, called cube vertices. Closed formulae are obtained to calculate the sum of shortest distances between pairs of cube vertices, between cube vertices and face centres and between pairs of face centres. Based on these formulae, their sum, the Wiener index of a face-centred cubic lattice with unit cells connected in a row graph, is computed.text/htmlWiener index on rows of unit cells of the face-centred cubic latticetext2722016-02-05Copyright (c) 2016 International Union of CrystallographyActa Crystallographica Section Aresearch papers00Aloysio Janner (1928–2016)
http://scripts.iucr.org/cgi-bin/paper?es0414
Copyright (c) 2016 International Union of Crystallographyurn:issn:2053-2733Janssen, T.2016-02-06doi:10.1107/S2053273316001935International Union of CrystallographyObituary for Aloysio Janner.ENobituarysuperspace groupsmathematical crystallographyaperiodic structuresquasicrystalstext/htmlAloysio Janner (1928–2016)text2722016-02-06Copyright (c) 2016 International Union of CrystallographyActa Crystallographica Section Aobituaries00Modern X-ray Analysis on Single Crystals. A Practical Guide. Second edition. By Peter Luger. De Gruyter, 2014. Pp. xi+334. Price EUR 119.95/USD 168.00/GBP 89.99. ISBN 978-3-11-030823-5.
http://scripts.iucr.org/cgi-bin/paper?xo0007
Copyright (c) 2016 International Union of Crystallographyurn:issn:2053-2733Lecomte, C.2016-02-05doi:10.1107/S205327331502121XInternational Union of CrystallographyENbook reviewX-ray analysissingle crystalstext/htmlModern X-ray Analysis on Single Crystals. A Practical Guide. Second edition. By Peter Luger. De Gruyter, 2014. Pp. xi+334. Price EUR 119.95/USD 168.00/GBP 89.99. ISBN 978-3-11-030823-5.text2722016-02-05Copyright (c) 2016 International Union of CrystallographyActa Crystallographica Section Abook reviews00Nominations for the Ewald Prize
http://scripts.iucr.org/cgi-bin/paper?es0415
Nominations for the 11th Ewald Prize are invited.Copyright (c) 2016 International Union of Crystallographyurn:issn:2053-2733Dacombe, M.2016-02-05doi:10.1107/S2053273316002096International Union of CrystallographyNominations for the 11th Ewald Prize are invited.ENEwald PrizeNominations for the 11th Ewald Prize are invited.text/htmlNominations for the Ewald Prizetext2722016-02-05Copyright (c) 2016 International Union of CrystallographyActa Crystallographica Section Ainternational union of crystallography00