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Journal logoSTRUCTURAL SCIENCE
CRYSTAL ENGINEERING
MATERIALS
ISSN: 2052-5206

June 2017 issue

Highlighted illustration

Cover illustration: Anion ordering of ATaO2N (bottom left: BaTaO2N; top right: SrTaO2N) from ideal disordered perovskite (top left) and with tilting of the octahedra in SrTaO2N (bottom right) [see Wang et al. (2017). Acta Cryst. B73, 389-398].

opinions


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Investigations are critically discussed where a toplogical analysis of the experimental charge density from single-crystal X-ray diffraction is the main result.

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The state of the art and the future of the topological analysis of experimental electron charge density is the topic of this perspective article, within a debate stimulated by a recent communication.

research papers


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A novel polar material, C5H6N3O2(HSO4), was synthesized, and its structure was determined in two phases. The origin of the X-ray diffuse scattering in a high-temperature disordered phase is explained as a precursor effect of the long-range ordered low-temperature phase.

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Intermolecular interactions in the bis­(L-asparaginium hydrogensquarate) monohydrate crystal are analyzed using Hirshfeld surface. The title compound has shown promising nonlinear optical and piezoelectric properties.

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The XRD pattern of a deleterious phase in the photocatalyst based on Cd1 − xZnxS/Zn(OH)2 contains two relatively intensive asymmetric peaks with d-spacings of 2.72 and 1.56 Å. To identify this phase, the XRD patterns were calculated for three models: sheet-like β-Zn(OH)2, sheet-like hydrozincite, Zn5(CO3)2(OH)6, and turbostratic hydrozincite. Simulations revealed the formation of a nanocrystalline turbostratic hydrozincite-like phase.

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The crystal structure of the mineral meneghinite, CuPb13Sb7S24, has been solved and refined as an incommensurate structure from X-ray single-crystal diffraction data in four-dimensional superspace. The very small departure from the commensurate value of the modulation raises the question of whether incommensurability in sulfosalts could be much more frequent than previously thought.

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A superspace model with complete vacancy ordering is presented based on X-ray diffraction of a 2/1 mullite sample with sharp satellite reflections. The results allow different conclusions of previous investigations of the last decades to be consolidated.

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Anion (O/N) ordering was observed in BaTaO2N and SrTaO2N. A further Ta—O/N octahedra displacement (rotation about the c axis) distortion was observed in SrTaO2N.


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The synthesis and the structural characterization of a cyclic hexapeptoid with four meth­oxy­ethyl and two propargyl side chains allows a discussion of the solid-state assembly of a hydrate crystal form (I) and an anhydrous crystal form (II). The relative amounts of forms (I) and (II) in the as-purified product were determined by Rietveld refinement and depend on the purification procedures.

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The frequently reported structure of Ni(Hpydc)2·3H2O (H2pydc = pyridine-2,6-dicarboxylic acid, also known as dipicolinic acid) is reinvestigated at temperatures ranging from 298 to 90 K. Strong hydrogen bonds are indicated.

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The clinopyroxene CaCuGe2O6 transforms from P21/cC2/c with increasing replacement of Cu2+ by Zn2+. The structural phase change is characterized using single-crystal X-ray diffraction and temperature-dependent Raman spectroscopy.

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Two iodidoantimonates(III), (C4H12N2)3[SbI6]2·5H2O and (C4H12N2)[SbI4]2·4H2O, obtained by reacting Sb2O3 and piperazine in hydroiodic acid, show different schemes of interactions: the hydrogen bonds in (C4H12N2)3[SbI6]2·5H2O form a network that favours the formation of significantly distorted isolated [SbI6]3– octahedra.

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The relationship between the chemical designation for helical polymeric molecules and the corresponding Hermann–Mauguin rod group symbols is analyzed, including interlocked multiple helices and helices of joined coordination polyhedra. The crystallographic rod subgroups of non-crystallographic rod groups are given.

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A computational approach for determining the chirality and stereoisomerism of chemical residues in crystallographic data entries is presented. The method is demonstrated for a dataset of 254 354 organic entries from the Cambridge Structural Database, revealing 409 kryptoracemates and 133 diastereomeric cocrystals.

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A new ternary scheelite tungstate (Sr, Ce)WO4 phase was synthesized, with a two-dimensional incommensurately modulated structure linked to partial ordering of Sr and Ce cations and vacancies as seen using high-resolution electron microscopy. A band gap of 3.2 eV makes it a promising violet-emitting compound.

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The interaction between strong donors (N—H, O—H) and carbon-bound fluorine is energetically favourable but very uncompetitive, a donor's last resort.

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Pyrroloquinoline quinol (PQQH2) and pyrroloquinoline quinone (PQQ) molecules play an important role as a cofactor in alcohol- and glucose-dehydrogenase reactions in bacteria. In the present study, the crystal structure analyses of PQQ and PQQH2 have been successfully elucidated for the first time.

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The structure of lithium niobate-tantalate has been studied using powder and single-crystal X-ray diffraction focusing on the composition and temperature induced zero-birefringence points.

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The formation of chiral crystals from achiral components, strong hydrogen-bond schemes and other structural properties of diaminium thio­sulfates are investigated and described. The conformations of α,ω-alkyl­diaminium cations in the solid state are analysed.
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