Introduction to Crystallography. By Frank Hoffmann. Springer, 2020. Hardback, pp. x+309. Price GBP 59.99. ISBN 9783030351090.
(Source: Acta Crystallographica Section A)
Source: Acta Crystallographica Section A - May 4, 2021 Category: Chemistry Authors: Nespolo, M. Tags: book review geometric crystallography book reviews Source Type: research
Electrons in Solids. Mesoscopics, Photonics, Quantum Computing, Correlations, Topology. By Hendrik Bluhm, Thomas Br ü ckel, Markus Morgenstern, Gero Plessen and Christoph Stampfer. De Gruyter, 2019. Paperback, pp. xii+393. Price EUR 59.95, USD 68.99, GBP 54.50. ISBN 978-3-11-043831-4.
(Source: Acta Crystallographica Section A)
Source: Acta Crystallographica Section A - May 4, 2021 Category: Chemistry Authors: Henkel, M. Tags: book review electrons in solids condensed matter physics book reviews Source Type: research
Bloch-wave interpretations of Gj ø nnes – Moodie lines in convergent-beam electron diffraction for non-symmorphic space-group crystals
The contrast of Gj ø nnes – Moodie (GM) lines which appear in convergent-beam electron diffraction patterns for non-symmorphic space-group crystals is explained using Bloch waves. In the two-dimensional space groups p2mg and pg the Bloch waves for electron diffraction are described. In both space groups along the Δ line, Bloch waves are arranged as two different types, and it is shown that the two types of Bloch waves do not contribute to the intensity of forbidden reflections. Along the position where the forbidden reflection satisfies the Bragg condition, degeneracies of two Bloch waves are found and it is shown that...
Source: Acta Crystallographica Section A - May 4, 2021 Category: Chemistry Authors: Matsuhata, H. Tags: many-beam dynamical electron diffraction Gj ø nnes – Moodie lines non-symmorphic space groups degeneracy of Bloch waves time-reversal degeneracy Herring criterion research papers Source Type: research
Combining X-rays, neutrons and electrons, and NMR, for precision and accuracy in structure – function studies
The distinctive features of the physics-based probes used in understanding the structure of matter focusing on biological sciences, but not exclusively, are described in the modern context. This is set in a wider scope of holistic biology and the scepticism about `reductionism', what is called the `molecular level', and how to respond constructively. These topics will be set alongside the principles of accuracy and precision, and their boundaries. The combination of probes and their application together is the usual way of realizing accuracy. The distinction between precision and accuracy can be blurred by the predictive f...
Source: Acta Crystallographica Section A - May 1, 2021 Category: Chemistry Authors: Helliwell, J.R. Tags: X-rays neutrons electrons NMR structure and function lead articles Source Type: research
A discussion on `Domain formation and phase transitions in the wurtzite-based heterovalent ternaries: a Landau theory analysis'
Heterovalent ternary nitrides are considered one of the promising classes of materials for photovoltaics, combining attractive physical properties with low toxicity and element abundance. One of the front-runner systems under consideration is ZnSnN2. Although it is nominally a ternary compound, no clear crystallographic evidence for cation ordering has been observed so far. An attempt to elucidate this discrepancy [Quayle (2020). Acta Cryst. A76, 410 – 420] was the trigger for an intensive discussion between the authors, and an agreement was reached to elaborate on some points in order to set things in perspective. Rathe...
Source: Acta Crystallographica Section A - March 23, 2021 Category: Chemistry Authors: Quayle, P.C. Breternitz, J. Tags: group – subgroup relationships nitride materials wurtzite type research papers Source Type: research
Symmetry relations in wurtzite nitrides and oxide nitrides and the curious case of Pmc21
Binary III – V nitrides such as AlN, GaN and InN in the wurtzite-type structure have long been considered as potent semiconducting materials because of their optoelectronic properties, amongst others. With rising concerns over the utilization of scarce elements, a replacement of the trivalent cations by others in ternary and multinary nitrides has led to the development of different variants of nitrides and oxide nitrides crystallizing in lower-symmetry variants of wurtzite. This work presents the symmetry relationships between these structural types specific to nitrides and oxide nitrides and updates some prior work on ...
Source: Acta Crystallographica Section A - March 23, 2021 Category: Chemistry Authors: Breternitz, J. Schorr, S. Tags: group – subgroup relationships nitride materials wurtzite type research papers Source Type: research
Diffraction line profiles from polydisperse crystalline systems. Corrigenda
Equation (16) and some entries in Table 1 in the article by Scardi& Leoni [(2001), Acta Cryst. A57, 604 – 613] are corrected. (Source: Acta Crystallographica Section A)
Source: Acta Crystallographica Section A - March 17, 2021 Category: Chemistry Authors: Scardi, P. Tags: line profile analysis LPA whole powder pattern modelling WPPM crystalline domain size corrigenda addenda and errata Source Type: research
A new electron diffraction approach for structure refinement applied to Ca3Mn2O7
The digital large-angle convergent-beam electron diffraction (D-LACBED) technique is applied to Ca3Mn2O7 for a range of temperatures. Bloch-wave simulations are used to examine the effects that changes in different parameters have on the intensity in D-LACBED patterns, and atomic coordinates, thermal atomic displacement parameters and apparent occupancy are refined to achieve a good fit between simulation and experiment. The sensitivity of the technique to subtle changes in structure is demonstrated. Refined structures are in good agreement with previous determinations of Ca3Mn2O7 and show the decay of anti-phase oxygen oc...
Source: Acta Crystallographica Section A - March 17, 2021 Category: Chemistry Authors: Beanland, R. Smith, K. Van ě k, P. Zhang, H. Hubert, A. Evans, K. R ö mer, R.A. Kamba, S. Tags: digital diffraction electron diffraction Ca3Mn2O7 CBED LACBED research papers Source Type: research
New perspectives in macromolecular powder diffraction using single-photon-counting strip detectors: high-resolution structure of the pharmaceutical peptide octreotide
In this study, in-line with past instrumental profile studies, an improved data collection strategy exploiting the MYTHEN II detector system together with significant beam focusing and tailored data collection options was introduced and optimized for protein samples at the Material Science beamline at the Swiss Light Source. Polycrystalline precipitates of octreotide, a somatostatin analog of particular pharmaceutical interest, were examined with this novel approach. XRPD experiments resulted in high angular and d-spacing (1.87 Å ) resolution data, from which electron-density maps of enhanced quality were extracted, r...
Source: Acta Crystallographica Section A - March 17, 2021 Category: Chemistry Authors: Spiliopoulou, M. Karavassili, F. Triandafillidis, D.-P. Valmas, A. Fili, S. Kosinas, C. Barlos, K. Barlos, K.K. Morin, M. Reinle-Schmitt, M.L. Gozzo, F. Margiolaki, I. Tags: octreotide MYTHEN II detector synchrotron X-ray powder diffraction research papers Source Type: research
Crystal symmetry for incommensurate helical and cycloidal modulations
A classification of magnetic superspace groups compatible with the helical and cycloidal magnetic modulations is presented. Helical modulations are compatible with groups from crystal classes 1, 2, 222, 4, 422, 3, 32, 6 and 622, while cycloidal modulations are compatible with groups from crystal classes 1, 2, m and mm2. For each magnetic crystal class, the directions of the symmetry-allowed (non-modulated) net ferromagnetic moment and electric polarization are given. The proposed classification of superspace groups is tested on experimental studies of type-II multiferroics published in the literature. (Source: Acta Crystal...
Source: Acta Crystallographica Section A - March 1, 2021 Category: Chemistry Authors: Fabrykiewicz, P. Przenios ł o, R. Sosnowska, I. Tags: symmetry magnetic ordering helical-type ordering screw-type ordering cycloidal-type ordering spiral-type ordering magnetic superspace groups multiferroics magnetoelectric coupling Dzialoshinsky – Moriya interaction research paper Source Type: research
X-ray dynamical diffraction Talbot effect behind a crystal in free space
The dynamical diffraction Talbot effect takes place inside a crystal, when a periodic object is illuminated by a plane or spherical X-ray wave which then falls on the crystal at an angle close to the Bragg angle for some reflection. Both theoretical consideration and numerical calculations show that the dynamical diffraction Talbot effect also takes place behind the crystal. The effect is accompanied by the dynamical diffraction pendulum effect and wave focusing. Expressions are found for the dynamical diffraction Talbot distance for areas before and after focusing. The spatial Fourier spectrum of the periodic object is ob...
Source: Acta Crystallographica Section A - March 1, 2021 Category: Chemistry Authors: Balyan, M. Levonyan, L. Trouni, K. Tags: Talbot effect dynamical diffraction X-rays crystals research papers Source Type: research
Coordination sequences of crystals are of quasi-polynomial type
The coordination sequence of a graph measures how many vertices the graph has at each distance from a fixed vertex and is a generalization of the coordination number. Here it is proved that the coordination sequence of the graph obtained from a crystal is of quasi-polynomial type, as had been postulated by Grosse-Kunstleve et al. [Acta Cryst. (1996), A52, 879 – 889]. (Source: Acta Crystallographica Section A)
Source: Acta Crystallographica Section A - February 18, 2021 Category: Chemistry Authors: Nakamura, Y. Sakamoto, R. Mase, T. Nakagawa, J. Tags: coordination sequences graph theory Hilbert polynomial monoid theory research papers Source Type: research
Isogonal piecewise linear embeddings of 1-periodic weaves and some related structures
Crystallographic descriptions of isogonal piecewise linear embeddings of 1-periodic weaves and links (chains) are presented. These are composed of straight segments (sticks) that meet at corners (2-valent vertices). Descriptions are also given of some plaits – woven periodic bands, three simple periodic knots and isogonal interwoven rods. (Source: Acta Crystallographica Section A)
Source: Acta Crystallographica Section A - February 5, 2021 Category: Chemistry Authors: O'Keeffe, M. Treacy, M.M.J. Tags: 1-periodic structures weaves links polycatenanes chains research papers Source Type: research
Arithmetic proof of the multiplicity-weighted Euler characteristic for symmetrically arranged space-filling polyhedra
The puzzling observation that the famous Euler's formula for three-dimensional polyhedra V − E + F = 2 or Euler characteristic χ = V − E + F − I = 1 (where V, E, F are the numbers of the bounding vertices, edges and faces, respectively, and I = 1 counts the single solid itself) when applied to space-filling solids, such as crystallographic asymmetric units or Dirichlet domains, are modified in such a way that they sum up to a value one unit smaller (i.e. to 1 or 0, respectively) is herewith given general validity. The proof provided in this paper for the modified Euler characteristic, χ m = Vm − Em + Fm − Im = ...
Source: Acta Crystallographica Section A - February 4, 2021 Category: Chemistry Authors: Naskr ę cki, B. Dauter, Z. Jaskolski, M. Tags: Euler's formula multiplicity-weighted Euler characteristic space-filling polyhedra polytopes asymmetric unit Dirichlet domains research papers Source Type: research
Spin-resolved atomic orbital model refinement for combined charge and spin density analysis: application to the YTiO3 perovskite
A new crystallographic method is proposed in order to refine a spin-resolved atomic orbital model against X-ray and polarized neutron diffraction data. This atomic orbital model is applied to the YTiO3 perovskite crystal, where orbital ordering has previously been observed by several techniques: X-ray diffraction, polarized neutron diffraction and nuclear magnetic resonance. This method gives the radial extension, orientation and population of outer atomic orbitals for each atom. The interaction term between Ti3+, Y3+ cations and O2 − ligands has been estimated. The refinement statistics obtained by means of the orbital ...
Source: Acta Crystallographica Section A - February 2, 2021 Category: Chemistry Authors: Kibalin, I. Voufack, A.B. Souhassou, M. Gillon, B. Gillet, J.-M. Claiser, N. Gukasov, A. Porcher, F. Lecomte, C. Tags: atomic orbital model two-center term polarized neutron diffraction X-ray diffraction perovskite spin density charge density research papers Source Type: research
