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) 2021 International Union of CrystallographyInternational Union of CrystallographyInternational Union of Crystallographyhttps://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) 2021 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 imageVanishing of the atomic form factor derivatives in non-spherical structural refinement – a key approximation scrutinized in the case of Hirshfeld atom refinement
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An investigation of the approximation, as used in non-spherical refinement, that the derivatives of the form factors are zero.Copyright (c) 2021 International Union of Crystallographyurn:issn:2053-2733Laura Midgley et al.doi:10.1107/S2053273321009086International Union of CrystallographyAn investigation of the approximation, as used in non-spherical refinement, that the derivatives of the form factors are zero.enQUANTUM CRYSTALLOGRAPHY; REFINEMENT; NON-SPHERICAL FORM FACTORSAn investigation of the approximation, as used in non-spherical refinement, that the derivatives of the form factors are zero.text/htmlVanishing of the atomic form factor derivatives in non-spherical structural refinement – a key approximation scrutinized in the case of Hirshfeld atom refinementtextParameterization of magnetic vector potentials and fields for efficient multislice calculations of elastic electron scattering
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Copyright (c) 2021 International Union of Crystallographyurn:issn:2053-2733Lyon and Ruszdoi:10.1107/S2053273321008792International Union of CrystallographyenMAGNETISM; MULTISLICE; PARAMETERIZATION; SIMULATION; DFTtext/htmlParameterization of magnetic vector potentials and fields for efficient multislice calculations of elastic electron scatteringtextCombinatorial aspects of the Löwenstein avoidance rule. Part I: the independence polynomial
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Practical issues concerning the calculation of independence ratios of finite graphs are analyzed.Copyright (c) 2021 International Union of Crystallographyurn:issn:2053-2733Moreira de Oliveira Jr and Eondoi:10.1107/S2053273321007956International Union of CrystallographyPractical issues concerning the calculation of independence ratios of finite graphs are analyzed.enNETS; QUOTIENT GRAPHS; INDEPENDENCE QUOTIENTPractical issues concerning the calculation of independence ratios of finite graphs are analyzed.text/htmlCombinatorial aspects of the Löwenstein avoidance rule. Part I: the independence polynomialtextLayer groups: Brillouin-zone and crystallographic databases on the Bilbao Crystallographic Server
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The set of databases of the Bilbao Crystallographic Server (https://www.cryst.ehu.es/) including crystallographic data on generators, general positions, Wyckoff positions, maximal subgroups and Brillouin-zone figures and k-vector tables for all 80 layer groups are discussed in detail and illustrated.Copyright (c) 2021 International Union of Crystallographyurn:issn:2053-2733Gemma de la Flor et al.doi:10.1107/S205327332100783XInternational Union of CrystallographyThe set of databases of the Bilbao Crystallographic Server (https://www.cryst.ehu.es/) including crystallographic data on generators, general positions, Wyckoff positions, maximal subgroups and Brillouin-zone figures and k-vector tables for all 80 layer groups are discussed in detail and illustrated.enBILBAO CRYSTALLOGRAPHIC SERVER; LAYER GROUPS; BRILLOUIN-ZONE DATABASEThe set of databases of the Bilbao Crystallographic Server (https://www.cryst.ehu.es/) including crystallographic data on generators, general positions, Wyckoff positions, maximal subgroups and Brillouin-zone figures and k-vector tables for all 80 layer groups are discussed in detail and illustrated.text/htmlLayer groups: Brillouin-zone and crystallographic databases on the Bilbao Crystallographic ServertextThe role of an objective function in the mathematical modelling of wide-angle X-ray diffraction curves of semi-crystalline polymers
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The choice of an objective function in constructing a mathematical model of an experimental wide-angle X-ray diffraction curve of semi-crystalline polymers is discussed.Copyright (c) 2021 International Union of Crystallographyurn:issn:2053-2733Rabiej and Rabiejdoi:10.1107/S2053273321007762International Union of CrystallographyThe choice of an objective function in constructing a mathematical model of an experimental wide-angle X-ray diffraction curve of semi-crystalline polymers is discussed.enPOLYMERS; DIFFRACTION CURVES; ABSOLUTE ERROR; RELATIVE ERROR; OBJECTIVE FUNCTION; MATHEMATICAL MODELLINGThe choice of an objective function in constructing a mathematical model of an experimental wide-angle X-ray diffraction curve of semi-crystalline polymers is discussed.text/htmlThe role of an objective function in the mathematical modelling of wide-angle X-ray diffraction curves of semi-crystalline polymerstextX-ray molecular orbital analysis. II. Application to diformohydrazide, (NHCHO)2
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The molecular orbitals of diformohydrazide were determined by X-ray molecular orbital analysis and it became evident that the molecular orbitals can be obtained by optimizing the electron density observed by X-ray diffraction.Copyright (c) 2021 International Union of Crystallographyurn:issn:2053-2733Tanaka and Wasada-Tsutsuidoi:10.1107/S2053273321006495International Union of CrystallographyThe molecular orbitals of diformohydrazide were determined by X-ray molecular orbital analysis and it became evident that the molecular orbitals can be obtained by optimizing the electron density observed by X-ray diffraction.enX-RAY MOLECULAR ORBITAL ANALYSIS; XMO ANALYSIS; ELECTRON DENSITY; MOLECULAR ORBITALS; DIFORMOHYDRAZIDE; MULTIPLE DIFFRACTION; HYDROGEN BONDSThe molecular orbitals of diformohydrazide were determined by X-ray molecular orbital analysis and it became evident that the molecular orbitals can be obtained by optimizing the electron density observed by X-ray diffraction.text/htmlX-ray molecular orbital analysis. II. Application to diformohydrazide, (NHCHO)2textThe wavevector star channel and symmetry group
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The concepts of `wavevector star channel' and `wavevector star channel group' are newly proposed, which allow the effective study of phase transitions by considering directly the translational symmetry breaking in crystals. It is shown that the complicated symmetry changes in the pyroelectric crystal Pb1−xCaxTiO3 (PCT) can be described using the new five-component reducible order parameter transformed according to the representation of the wavevector star channel group but not the nine-component one based on the theory of the full irreducible representation of the space group.Copyright (c) 2021 International Union of Crystallographyurn:issn:2053-2733Il-Hwan Kim et al.doi:10.1107/S2053273321006318International Union of CrystallographyThe concepts of `wavevector star channel' and `wavevector star channel group' are newly proposed, which allow the effective study of phase transitions by considering directly the translational symmetry breaking in crystals. It is shown that the complicated symmetry changes in the pyroelectric crystal Pb1−xCaxTiO3 (PCT) can be described using the new five-component reducible order parameter transformed according to the representation of the wavevector star channel group but not the nine-component one based on the theory of the full irreducible representation of the space group.enWAVEVECTOR STAR CHANNELS; WAVEVECTOR STAR CHANNEL GROUPS; TRANSLATIONAL SYMMETRY BREAKING; PHASE TRANSITIONS; LEAD CALCIUM TITANATE; PB1-XCAXTIO3; PCTThe concepts of `wavevector star channel' and `wavevector star channel group' are newly proposed, which allow the effective study of phase transitions by considering directly the translational symmetry breaking in crystals. It is shown that the complicated symmetry changes in the pyroelectric crystal Pb1−xCaxTiO3 (PCT) can be described using the new five-component reducible order parameter transformed according to the representation of the wavevector star channel group but not the nine-component one based on the theory of the full irreducible representation of the space group.text/htmlThe wavevector star channel and symmetry grouptext