Acta Crystallographica Section A
http://journals.iucr.org/a/issues/2015/01/00/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) 2015 International Union of Crystallography2014-12-18International 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 71, Part 1, 2015textyearly62002-01-01T00:00+00:001712014-12-18Copyright (c) 2015 International Union of CrystallographyActa Crystallographica Section A: Foundations and Advances1urn:issn:2053-2733med@iucr.orgDecember 20142014-12-18Acta Crystallographica Section Ahttp://journals.iucr.org/logos/rss10a.gif
http://journals.iucr.org/a/issues/2015/01/00/isscontsbdy.html
Still imageNuclear-weighted X-ray maximum entropy method – NXMEM
http://scripts.iucr.org/cgi-bin/paper?ib5029
Subtle structural features such as disorder and anharmonic motion may be accurately characterized from nuclear density distributions (NDDs). As a viable alternative to neutron diffraction, this paper introduces a new approach named the nuclear-weighted X-ray maximum entropy method (NXMEM) for reconstructing pseudo NDDs. It calculates an electron-weighted nuclear density distribution (eNDD), exploiting that X-ray diffraction delivers data of superior quality, requires smaller sample volumes and has higher availability. NXMEM is tested on two widely different systems: PbTe and Ba8Ga16Sn30. The first compound, PbTe, possesses a deceptively simple crystal structure on the macroscopic level that is unable to account for its excellent thermoelectric properties. The key mechanism involves local distortions, and the capability of NXMEM to probe this intriguing feature is established with simulated powder diffraction data. In the second compound, Ba8Ga16Sn30, disorder among the Ba guest atoms is analysed with both experimental and simulated single-crystal diffraction data. In all cases, NXMEM outperforms the maximum entropy method by substantially enhancing the nuclear resolution. The induced improvements correlate with the amount of available data, rendering NXMEM especially powerful for powder and low-resolution single-crystal diffraction. The NXMEM procedure can be implemented in existing software and facilitates widespread characterization of disorder in functional materials.Copyright (c) 2015 International Union of Crystallographyurn:issn:2053-2733Christensen, S.Bindzus, N.Christensen, M.Brummerstedt Iversen, B.2015-01-01doi:10.1107/S2053273314024103International Union of CrystallographyNXMEM is a new method to reconstruct pseudo nuclear-density distributions from X-ray diffraction data. It is validated against simulated and experimental data on two disordered systems, PbTe and Ba8Ga16Sn30.ENmaximum entropy methodX-ray diffractiondisordered structuresnuclear density distributionthermoelectricityPbTeclathratesBa8Ga16Sn30Subtle structural features such as disorder and anharmonic motion may be accurately characterized from nuclear density distributions (NDDs). As a viable alternative to neutron diffraction, this paper introduces a new approach named the nuclear-weighted X-ray maximum entropy method (NXMEM) for reconstructing pseudo NDDs. It calculates an electron-weighted nuclear density distribution (eNDD), exploiting that X-ray diffraction delivers data of superior quality, requires smaller sample volumes and has higher availability. NXMEM is tested on two widely different systems: PbTe and Ba8Ga16Sn30. The first compound, PbTe, possesses a deceptively simple crystal structure on the macroscopic level that is unable to account for its excellent thermoelectric properties. The key mechanism involves local distortions, and the capability of NXMEM to probe this intriguing feature is established with simulated powder diffraction data. In the second compound, Ba8Ga16Sn30, disorder among the Ba guest atoms is analysed with both experimental and simulated single-crystal diffraction data. In all cases, NXMEM outperforms the maximum entropy method by substantially enhancing the nuclear resolution. The induced improvements correlate with the amount of available data, rendering NXMEM especially powerful for powder and low-resolution single-crystal diffraction. The NXMEM procedure can be implemented in existing software and facilitates widespread characterization of disorder in functional materials.text/htmlNuclear-weighted X-ray maximum entropy method – NXMEMtext1712015-01-01Copyright (c) 2015 International Union of CrystallographyActa Crystallographica Section Aresearch papers00Diffuse multiple scattering
http://scripts.iucr.org/cgi-bin/paper?td5022
A new form of diffraction lines has been identified, similar to Rutherford, Kikuchi and Kossel lines. This paper highlights some of the properties of these lines and shows how they can be used to eliminate the need for sample/source matching in Lonsdale's triple convergent line method in lattice-parameter determination.Copyright (c) 2015 A. G. A. Nisbet et al.urn:issn:2053-2733Nisbet, A.G.A.Beutier, G.Fabrizi, F.Moser, B.Collins, S.P.2015-01-01doi:10.1107/S2053273314026515International Union of CrystallographyA new form of diffraction lines similar to Rutherford, Kikuchi and Kossel lines has been identified. They can be used to eliminate the need for sample/source matching in Lonsdale's triple convergent line method in lattice-parameter determination.ENdiffuse scatteringmultiple scatteringKossel linesKikuchi linesstrainlattice parametersA new form of diffraction lines has been identified, similar to Rutherford, Kikuchi and Kossel lines. This paper highlights some of the properties of these lines and shows how they can be used to eliminate the need for sample/source matching in Lonsdale's triple convergent line method in lattice-parameter determination.text/htmlDiffuse multiple scatteringtext1712015-01-01Copyright (c) 2015 A. G. A. Nisbet et al.Acta Crystallographica Section Aresearch papers00Prediction of molecular crystal structures by a crystallographic QM/MM model with full space-group symmetry
http://scripts.iucr.org/cgi-bin/paper?kx5031
A crystallographic quantum-mechanical/molecular-mechanical model (c-QM/MM model) with full space-group symmetry has been developed for molecular crystals. The lattice energy was calculated by quantum-mechanical methods for short-range interactions and force-field methods for long-range interactions. The quantum-mechanical calculations covered the interactions within the molecule and the interactions of a reference molecule with each of the surrounding 12–15 molecules. The interactions with all other molecules were treated by force-field methods. In each optimization step the energies in the QM and MM shells were calculated separately as single-point energies; after adding both energy contributions, the crystal structure (including the lattice parameters) was optimized accordingly. The space-group symmetry was maintained throughout. Crystal structures with more than one molecule per asymmetric unit, e.g. structures with Z′ = 2, hydrates and solvates, have been optimized as well. Test calculations with different quantum-mechanical methods on nine small organic molecules revealed that the density functional theory methods with dispersion correction using the B97-D functional with 6-31G* basis set in combination with the DREIDING force field reproduced the experimental crystal structures with good accuracy. Subsequently the c-QM/MM method was applied to nine compounds from the CCDC blind tests resulting in good energy rankings and excellent geometric accuracies.Copyright (c) 2015 International Union of Crystallographyurn:issn:2053-2733Mörschel, P.Schmidt, M.U.2015-01-01doi:10.1107/S2053273314018907International Union of CrystallographyA new crystallographic quantum-mechanical/molecular-mechanical model for the prediction of molecular crystal structures is described. Applications include polymorphic systems and molecules from the CCDC blind tests of crystal structure prediction.ENcrystal structure predictionquantum mechanics/molecular mechanicsdensity functional theoryblind testA crystallographic quantum-mechanical/molecular-mechanical model (c-QM/MM model) with full space-group symmetry has been developed for molecular crystals. The lattice energy was calculated by quantum-mechanical methods for short-range interactions and force-field methods for long-range interactions. The quantum-mechanical calculations covered the interactions within the molecule and the interactions of a reference molecule with each of the surrounding 12–15 molecules. The interactions with all other molecules were treated by force-field methods. In each optimization step the energies in the QM and MM shells were calculated separately as single-point energies; after adding both energy contributions, the crystal structure (including the lattice parameters) was optimized accordingly. The space-group symmetry was maintained throughout. Crystal structures with more than one molecule per asymmetric unit, e.g. structures with Z′ = 2, hydrates and solvates, have been optimized as well. Test calculations with different quantum-mechanical methods on nine small organic molecules revealed that the density functional theory methods with dispersion correction using the B97-D functional with 6-31G* basis set in combination with the DREIDING force field reproduced the experimental crystal structures with good accuracy. Subsequently the c-QM/MM method was applied to nine compounds from the CCDC blind tests resulting in good energy rankings and excellent geometric accuracies.text/htmlPrediction of molecular crystal structures by a crystallographic QM/MM model with full space-group symmetrytext1712015-01-01Copyright (c) 2015 International Union of CrystallographyActa Crystallographica Section Aresearch papers00From direct-space discrepancy functions to crystallographic least squares
http://scripts.iucr.org/cgi-bin/paper?mq5027
Crystallographic least squares are a fundamental tool for crystal structure analysis. In this paper their properties are derived from functions estimating the degree of similarity between two electron-density maps. The new approach leads also to modifications of the standard least-squares procedures, potentially able to improve their efficiency. The role of the scaling factor between observed and model amplitudes is analysed: the concept of unlocated model is discussed and its scattering contribution is combined with that arising from the located model. Also, the possible use of an ancillary parameter, to be associated with the classical weight related to the variance of the observed amplitudes, is studied. The crystallographic discrepancy factors, basic tools often combined with least-squares procedures in phasing approaches, are analysed. The mathematical approach here described includes, as a special case, the so-called vector refinement, used when accurate estimates of the target phases are available.Copyright (c) 2015 International Union of Crystallographyurn:issn:2053-2733Giacovazzo, C.2015-01-01doi:10.1107/S2053273314019056International Union of CrystallographyCrystallographic least-squares properties are derived from discrepancy functions working in direct space.ENleast squaresscaling factorsunlocated modelsvector refinementCrystallographic least squares are a fundamental tool for crystal structure analysis. In this paper their properties are derived from functions estimating the degree of similarity between two electron-density maps. The new approach leads also to modifications of the standard least-squares procedures, potentially able to improve their efficiency. The role of the scaling factor between observed and model amplitudes is analysed: the concept of unlocated model is discussed and its scattering contribution is combined with that arising from the located model. Also, the possible use of an ancillary parameter, to be associated with the classical weight related to the variance of the observed amplitudes, is studied. The crystallographic discrepancy factors, basic tools often combined with least-squares procedures in phasing approaches, are analysed. The mathematical approach here described includes, as a special case, the so-called vector refinement, used when accurate estimates of the target phases are available.text/htmlFrom direct-space discrepancy functions to crystallographic least squarestext1712015-01-01Copyright (c) 2015 International Union of CrystallographyActa Crystallographica Section Aresearch papers00Analysis of rapidly synthesized guest-filled porous complexes with synchrotron radiation: practical guidelines for the crystalline sponge method
http://scripts.iucr.org/cgi-bin/paper?pc5042
A detailed set of synthetic and crystallographic guidelines for the crystalline sponge method based upon the analysis of expediently synthesized crystal sponges using third-generation synchrotron radiation are reported. The procedure for the synthesis of the zinc-based metal–organic framework used in initial crystal sponge reports has been modified to yield competent crystals in 3 days instead of 2 weeks. These crystal sponges were tested on some small molecules, with two being unexpectedly difficult cases for analysis with in-house diffractometers in regard to data quality and proper space-group determination. These issues were easily resolved by the use of synchrotron radiation using data-collection times of less than an hour. One of these guests induced a single-crystal-to-single-crystal transformation to create a larger unit cell with over 500 non-H atoms in the asymmetric unit. This led to a non-trivial refinement scenario that afforded the best Flack x absolute stereochemical determination parameter to date for these systems. The structures did not require the use of PLATON/SQUEEZE or other solvent-masking programs, and are the highest-quality crystalline sponge systems reported to date where the results are strongly supported by the data. A set of guidelines for the entire crystallographic process were developed through these studies. In particular, the refinement guidelines include strategies to refine the host framework, locate guests and determine occupancies, discussion of the proper use of geometric and anisotropic displacement parameter restraints and constraints, and whether to perform solvent squeezing/masking. The single-crystal-to-single-crystal transformation process for the crystal sponges is also discussed. The presented general guidelines will be invaluable for researchers interested in using the crystalline sponge method at in-house diffraction or synchrotron facilities, will facilitate the collection and analysis of reliable high-quality data, and will allow construction of chemically and physically sensible models for guest structural determination.Copyright (c) 2015 International Union of Crystallographyurn:issn:2053-2733Ramadhar, T.R.Zheng, S.-L.Chen, Y.-S.Clardy, J.2015-01-01doi:10.1107/S2053273314019573International Union of CrystallographyThis report describes complete practical guidelines and insights for the crystalline sponge method, which have been derived through the first use of synchrotron radiation on these systems, and includes a procedure for faster synthesis of the sponges. These guidelines will be applicable to crystal sponge data collected at synchrotrons or in-house facilities, and will allow researchers to obtain reliable high-quality data and construct chemically and physically sensible models for guest structural determination.ENX-ray crystallographycrystalline sponge methodmetal–organic frameworksingle-crystal-to-single-crystal transformationsynchrotron radiationA detailed set of synthetic and crystallographic guidelines for the crystalline sponge method based upon the analysis of expediently synthesized crystal sponges using third-generation synchrotron radiation are reported. The procedure for the synthesis of the zinc-based metal–organic framework used in initial crystal sponge reports has been modified to yield competent crystals in 3 days instead of 2 weeks. These crystal sponges were tested on some small molecules, with two being unexpectedly difficult cases for analysis with in-house diffractometers in regard to data quality and proper space-group determination. These issues were easily resolved by the use of synchrotron radiation using data-collection times of less than an hour. One of these guests induced a single-crystal-to-single-crystal transformation to create a larger unit cell with over 500 non-H atoms in the asymmetric unit. This led to a non-trivial refinement scenario that afforded the best Flack x absolute stereochemical determination parameter to date for these systems. The structures did not require the use of PLATON/SQUEEZE or other solvent-masking programs, and are the highest-quality crystalline sponge systems reported to date where the results are strongly supported by the data. A set of guidelines for the entire crystallographic process were developed through these studies. In particular, the refinement guidelines include strategies to refine the host framework, locate guests and determine occupancies, discussion of the proper use of geometric and anisotropic displacement parameter restraints and constraints, and whether to perform solvent squeezing/masking. The single-crystal-to-single-crystal transformation process for the crystal sponges is also discussed. The presented general guidelines will be invaluable for researchers interested in using the crystalline sponge method at in-house diffraction or synchrotron facilities, will facilitate the collection and analysis of reliable high-quality data, and will allow construction of chemically and physically sensible models for guest structural determination.text/htmlAnalysis of rapidly synthesized guest-filled porous complexes with synchrotron radiation: practical guidelines for the crystalline sponge methodtext1712015-01-01Copyright (c) 2015 International Union of CrystallographyActa Crystallographica Section Aresearch papers001007931100792910079301007932The anatomy of a comprehensive constrained, restrained refinement program for the modern computing environment – Olex2 dissected
http://scripts.iucr.org/cgi-bin/paper?pc5043
This paper describes the mathematical basis for olex2.refine, the new refinement engine which is integrated within the Olex2 program. Precise and clear equations are provided for every computation performed by this engine, including structure factors and their derivatives, constraints, restraints and twinning; a general overview is also given of the different components of the engine and their relation to each other. A framework for adding multiple general constraints with dependencies on common physical parameters is described. Several new restraints on atomic displacement parameters are also presented.Copyright (c) 2015 Luc J. Bourhis et al.urn:issn:2053-2733Bourhis, L.J.Dolomanov, O.V.Gildea, R.J.Howard, J.A.K.Puschmann, H.2015-01-01doi:10.1107/S2053273314022207International Union of CrystallographyAn in-depth presentation is given of olex2.refine, the new refinement engine integrated in the Olex2 program.ENsmall moleculesrefinementconstraintsrestraintsleast squaresOlex2This paper describes the mathematical basis for olex2.refine, the new refinement engine which is integrated within the Olex2 program. Precise and clear equations are provided for every computation performed by this engine, including structure factors and their derivatives, constraints, restraints and twinning; a general overview is also given of the different components of the engine and their relation to each other. A framework for adding multiple general constraints with dependencies on common physical parameters is described. Several new restraints on atomic displacement parameters are also presented.text/htmlThe anatomy of a comprehensive constrained, restrained refinement program for the modern computing environment – Olex2 dissectedtext1712015-01-01Copyright (c) 2015 Luc J. Bourhis et al.Acta Crystallographica Section Aresearch papers00An alternative method for the calculation of joint probability distributions. Application to the expectation of the triplet invariant
http://scripts.iucr.org/cgi-bin/paper?sc5080
This paper presents a completely new method for the calculation of expectations (and thus joint probability distributions) of structure factors or phase invariants. As an example, a first approximation of the expectation of the triplet invariant (up to a constant) is given and a complex number is obtained. Instead of considering the atomic vector positions or reciprocal vectors as the fundamental random variables, the method samples over all functions (distributions) with a given number of atoms and given Patterson function. The aim of this paper was to explore the feasibility of the method, so the easiest problem was chosen: the calculation of the expectation value of the triplet invariant in P1. Calculation of the joint probability distribution of the triplet is not performed here but will be done in the future.Copyright (c) 2015 International Union of Crystallographyurn:issn:2053-2733Brosius, J.2015-01-01doi:10.1107/S2053273314023560International Union of CrystallographyAn explanation is given of the method for the calculation of expectation values by sampling over atomic distributions.ENfunctional integrationdirect methodsphase determinationThis paper presents a completely new method for the calculation of expectations (and thus joint probability distributions) of structure factors or phase invariants. As an example, a first approximation of the expectation of the triplet invariant (up to a constant) is given and a complex number is obtained. Instead of considering the atomic vector positions or reciprocal vectors as the fundamental random variables, the method samples over all functions (distributions) with a given number of atoms and given Patterson function. The aim of this paper was to explore the feasibility of the method, so the easiest problem was chosen: the calculation of the expectation value of the triplet invariant in P1. Calculation of the joint probability distribution of the triplet is not performed here but will be done in the future.text/htmlAn alternative method for the calculation of joint probability distributions. Application to the expectation of the triplet invarianttext1712015-01-01Copyright (c) 2015 International Union of CrystallographyActa Crystallographica Section Aresearch papers00High-symmetry embeddings of interpenetrating periodic nets. Essential rings and patterns of catenation
http://scripts.iucr.org/cgi-bin/paper?eo5041
Symmetrical embeddings are given for multiply intergrown sets of some commonly occurring nets such as dia (diamond), qtz (quartz), pcu (net of primitive cubic lattice) and srs (labyrinth net of the G minimal surface). Data are also given for all known pairs of nets which have edge-transitive self-dual tilings. Examples are given for symmetrical polycatenation of the 2-periodic nets sql (square lattice) and hcb (honeycomb). The idea that the rings that are the faces of natural tilings form a complete basis set (essential rings) is explored and patterns of catenation of such rings described.Copyright (c) 2015 International Union of Crystallographyurn:issn:2053-2733Bonneau, C.O'Keeffe, M.2015-01-01doi:10.1107/S2053273314019950International Union of CrystallographyCrystallographic and catenation data are given for embeddings of interpenetrating sets of common 2- and 3-periodic nets.ENperiodic netsinterpenetrating netscatenationpolycatenationSymmetrical embeddings are given for multiply intergrown sets of some commonly occurring nets such as dia (diamond), qtz (quartz), pcu (net of primitive cubic lattice) and srs (labyrinth net of the G minimal surface). Data are also given for all known pairs of nets which have edge-transitive self-dual tilings. Examples are given for symmetrical polycatenation of the 2-periodic nets sql (square lattice) and hcb (honeycomb). The idea that the rings that are the faces of natural tilings form a complete basis set (essential rings) is explored and patterns of catenation of such rings described.text/htmlHigh-symmetry embeddings of interpenetrating periodic nets. Essential rings and patterns of catenationtext1712015-01-01Copyright (c) 2015 International Union of CrystallographyActa Crystallographica Section Aresearch papers00Direct phasing of protein crystals with high solvent content
http://scripts.iucr.org/cgi-bin/paper?mq5029
An iterative transform method is proposed for solving the phase problem in protein crystallography. In each iteration, a weighted average electron-density map is constructed to define an estimated protein mask. Solvent flattening is then imposed through the hybrid input–output algorithm [Fienup (1982). Appl. Opt. 21, 2758–2769]. Starting from random initial phases, after thousands of iterations the mask evolves into the correct shape and the phases converge to the correct values with an average error of 30–40° for high-resolution data for several protein crystals with high solvent content. With the use of non-crystallographic symmetry, the method could potentially be extended to phase protein crystals with less than 50% solvent fraction. The new phasing algorithm can supplement and enhance the traditional refinement tools.Copyright (c) 2015 International Union of Crystallographyurn:issn:2053-2733He, H.Su, W.-P.2015-01-01doi:10.1107/S2053273314024097International Union of CrystallographyAn iterative transform algorithm is proposed for extracting the phases of X-ray reflections directly from the diffraction intensity data of protein crystals with high solvent content. Examples of successful trial calculations carried out with real diffraction data are presented.ENab initio phasingprotein crystallographyhybrid input–output algorithmsolvent flatteningAn iterative transform method is proposed for solving the phase problem in protein crystallography. In each iteration, a weighted average electron-density map is constructed to define an estimated protein mask. Solvent flattening is then imposed through the hybrid input–output algorithm [Fienup (1982). Appl. Opt. 21, 2758–2769]. Starting from random initial phases, after thousands of iterations the mask evolves into the correct shape and the phases converge to the correct values with an average error of 30–40° for high-resolution data for several protein crystals with high solvent content. With the use of non-crystallographic symmetry, the method could potentially be extended to phase protein crystals with less than 50% solvent fraction. The new phasing algorithm can supplement and enhance the traditional refinement tools.text/htmlDirect phasing of protein crystals with high solvent contenttext1712015-01-01Copyright (c) 2015 International Union of CrystallographyActa Crystallographica Section Aresearch papers00Symmetry groups associated with tilings on a flat torus
http://scripts.iucr.org/cgi-bin/paper?eo5038
This work investigates symmetry and color symmetry properties of Kepler, Heesch and Laves tilings embedded on a flat torus and their geometric realizations as tilings on a round torus in Euclidean 3-space. The symmetry group of the tiling on the round torus is determined by analyzing relevant symmetries of the planar tiling that are transformed to axial symmetries of the three-dimensional tiling. The focus on studying tilings on a round torus is motivated by applications in the geometric modeling of nanotori and the determination of their symmetry groups.Copyright (c) 2015 International Union of Crystallographyurn:issn:2053-2733Loyola, M.L.De Las Peñas, M.L.A.N.Estrada, G.M.Santoso, E.B.2015-01-01doi:10.1107/S205327331402419XInternational Union of CrystallographyThis work investigates the symmetry and color-symmetry properties of transitive tilings embedded on a flat torus and their geometric realizations as tilings on a round torus. The realizations are used to model nanotori.ENnanotoriflat torussymmetry groupscolor symmetryThis work investigates symmetry and color symmetry properties of Kepler, Heesch and Laves tilings embedded on a flat torus and their geometric realizations as tilings on a round torus in Euclidean 3-space. The symmetry group of the tiling on the round torus is determined by analyzing relevant symmetries of the planar tiling that are transformed to axial symmetries of the three-dimensional tiling. The focus on studying tilings on a round torus is motivated by applications in the geometric modeling of nanotori and the determination of their symmetry groups.text/htmlSymmetry groups associated with tilings on a flat torustext1712015-01-01Copyright (c) 2015 International Union of CrystallographyActa Crystallographica Section Aresearch papers00Scanning of two-dimensional space groups
http://scripts.iucr.org/cgi-bin/paper?td5021
Tables of the scanning of two-dimensional space groups are presented to determine the frieze-group symmetry of lines that transect two-dimensional crystals. It is shown how these tables can be used to predict the (001) projection symmetries of migration-related segments of coincidence site lattice tilt boundaries with [001] tilt axis.Copyright (c) 2015 International Union of Crystallographyurn:issn:2053-2733Litvin, D.B.2015-01-01doi:10.1107/S2053273314022384International Union of CrystallographyScanning tables of two-dimensional space groups are presented.ENscanningfrieze groupstwo-dimensional space groupsTables of the scanning of two-dimensional space groups are presented to determine the frieze-group symmetry of lines that transect two-dimensional crystals. It is shown how these tables can be used to predict the (001) projection symmetries of migration-related segments of coincidence site lattice tilt boundaries with [001] tilt axis.text/htmlScanning of two-dimensional space groupstext1712015-01-01Copyright (c) 2015 International Union of CrystallographyActa Crystallographica Section Ashort communications00Report of the Executive Committee for 2013
http://scripts.iucr.org/cgi-bin/paper?es0406
The report of the Executive Committee for 2013 is presented.Copyright (c) 2015 International Union of Crystallographyurn:issn:2053-2733Dacombe, M.2015-01-01doi:10.1107/S2053273314015484International Union of CrystallographyThe report of the Executive Committee for 2013 is presented.ENReport of the Executive CommitteeThe report of the Executive Committee for 2013 is presented.text/htmlReport of the Executive Committee for 2013text1712015-01-01Copyright (c) 2015 International Union of CrystallographyActa Crystallographica Section Ainternational union of crystallography00