issue contents

Journal logoSTRUCTURAL SCIENCE
CRYSTAL ENGINEERING
MATERIALS
ISSN: 2052-5206

October 2006 issue

Highlighted illustration

Cover illustration: Room-temperature structure of the cation-deficient perovskite, Nd0.7Ti0.9Al0.1O3 [Zhang et al. (2006). Acta Cryst. B62, 60-67>]. The superlattice peaks associated with out-of-phase octahedral tilting (shown) have intensities consistent with tilting around the x and y axes (sum of a- and c-), but tilting around the y axis (contribution b-) evidently does not occur. The tilt system in Glazer's notation is thus a-b0c-, and the space group and structure are found from the tree displayed. Two views of the structure are shown - the (TiAl)O6 are shown as octahedra, the Ti/Al atom being visible within them, and the darker and lighter spheres outside these octahedra represent fully and partly occupied layers of Nd, respectively. The octahedral tilting, around both x and y axes, is clearly seen.

research papers


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An analysis of the Flack parameter based on published (pseudo-)centrosymmetric crystal-structure determinations.

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More precise bond-valence parameters d0 of B—O bonds are recommended for various kinds of fundamental building blocks (FBBs) in borates, considering dominant factors such as the detailed configurations of borate FBBs, anhydrous or hydrous, the interstitial halogen anions, and the substitution of borate anions. Current structural analysis may be helpful for us to search for novel nonlinear optical borates.

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We report the crystal structure analyses of CaAlSi from single-crystal and powder X-ray diffraction and the existence of two commensurately modulated structures.

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The crystal structure of TlH2PO4 (TDP) has been studied at low temperatures. Lattice parameters were derived from high-resolution X-ray powder diffraction in the temperature range between 8 and 300 K. A detailed crystal structure analysis of the antiferroelectric low-temperature phase (TDP-III) has been performed based on neutron diffraction data measured at 210 K. The polymorphism of TDP and the fully deuterated TlD2PO4 (DTDP) is presented in the form of group–subgroup relations between the different space groups.

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This work reports the structural characterization of very thin Ni2Si layers grown at low temperature by transrotational domains. A non-conventional mechanism of strain relaxation has been proposed, which is competitive with respect to the usual formation of misfit dislocations, consisting of Ni2Si lattice bending and rearrangement of the interface to minimize the Gibbs free energy of the domain.

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An ideal (3 + 1)-dimensional model was proposed for the homologous series Ga4Tim−4O2m−2 with crystallographic shear structures based on that of rutile. The Rietveld fitting of the X-ray diffraction profile of Ga4Ti13O32 was performed using the model.

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Ln—O and Ln—N bond-valence parameters of four classical `not trivalent' elements (CeIV, SmII, EuII and YbII), and Ln—Cl, Ln—S and Ln—C(π-bonded) bond-valence parameters are presented, as calculated for coordination compounds.

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Using the Voronoi–Dirichlet polyhedra and the method of intersecting spheres, 2917 compounds containing 3903 crystallographically non-equivalent types of LnOn polyhedron (Ln = La–Lu) were analyzed. Despite a great diversity in coordination numbers and types of coordination polyhedra, the volume of the Voronoi–Dirichlet polyhedron of an Ln atom was found to depend only on the identity of the Ln atom and its oxidation state.

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Special twin boundaries in monoclinic zirconia phases doped with different trivalent cations of rare earths are characterized in detail. The suitability of using selected-area diffraction patterns for this kind of study is demonstrated.

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The crystal structure of a natural Se-rich antimonpearceite, [(Ag,Cu)6(Sb,As)2(S,Se)7][Ag9Cu(S,Se)2Se2], has been solved and refined from X-ray single-crystal diffraction data at room temperature in its ionic-conducting form and at 120 K in its non-conducting ordered form.

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The structure of levyclaudite-(Sb), a member of the cylindrite mineral group, has been determined from a synthetic sample by single-crystal X-ray diffraction on the basis of the (3 + 2)-dimensional superspace approach.

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The syntheses and structure determinations by means of single-crystal X-ray diffraction of commensurate (C6H14N2)2[Mo8O26]·4H2O and incommensurate (C6H14N2)2[Mo8O26]·4.66H2O, two new organic–inorganic hybrid compounds based on polyoxomolybdates, are reported.

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Among a family of related structures, a single-crystal neutron diffraction study was carried out on a fully deuterated potassium cyanurate complex to study potential deuterium-atom disorder. Instead it revealed that the true unit cell is a supercell of that identified by X-rays, corresponding to the doubling of one axis, caused by just two deuterium atoms which break apparent crystallographically imposed mirror symmetry.

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Metal-organic framework structures adopting either square grid or triangular grid architectures are reported. A family of the latter type incorporating different solvent molecules sheds light on the flexibility of these layered structures in previously reported solvent loss/uptake.

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The hydrostatic compression of L-serine-d7 has been studied to 8.1 GPa by neutron powder diffraction. Over the course of this pressure range the compound undergoes two phase transitions, the first between 4.6 and 5.2 GPa, and the second between 7.3 and 8.1 GPa.

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Recrystallization from a dichloromethane solution at 0.5 GPa affords new polymorphs of phenanthrene and pyrene. Structural analysis of the high-pressure polymorphs of pyrene and phenanthrene shows that intermolecular interactions are substantially different from those found in the ambient-pressure structures and do not fit a previously established packing model for polycyclic aromatic hydrocarbons. Recrystallization of naphthalene from a dichloromethane solution in the 0.2–0.6 GPa pressure range does not result in the formation of a new polymorph, and its crystal structure is reported to be stable to compression to 2.1 GPa.


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In typical intramolecular resonance-assisted hydrogen bonds (RAHBs), enolones (⋯O=C—C=C—OH⋯) and enaminones (⋯O=C—C=C—NH⋯) form π-cooperative six-membered rings closed by strong O—H⋯O or N—H⋯O bonds. This paper studies the ways of fusion of two of these rings through a common C=O or C—C bond, and shows that such a fusion gives rise to unusual forms of prototropic tautomerism whose relative energies can be explained in terms of π-cooperative and π-anticooperative relationships of the two cumulated RAHBs.

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The crystal structures of triethyl-1,3,5-triazine-2,4,6-tricarboxylate, triethyl-1,3,5-benzenetricarboxylate and tris-2-hydroxyethyl isocyanurate have been determined from laboratory X-ray powder and single-crystal diffraction data, despite the presence of disorder and significant preferred orientation. The materials display contrasting packing behaviour, with only the triazine derivative retaining threefold molecular symmetry in its crystal structure.

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Ab initio ONIOM cluster calculations are combined with TLS analysis of heavy-atom ADPs from X-ray diffraction data to provide accurate estimates of H-atom ADPs for charge-density analysis.

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Structural characterization of two new monocyclic and linear human tachykinin NK-2 antagonists showing the β-turn feature.

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The positions of molecular pairs in structures with Z′ = 2 are considered for space groups common for that class of structure in the Cambridge Structural Database.

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The geometry of hydrogen bonds in 1,6-anhydro-β-D-glucopyranose is accurately determined by single-crystal neutron diffraction. DFT calculations predict red (blue) shifts of stretching frequencies of O—H (C—H) in this material due to the formation of hydrogen bonds.

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The crystal structure of triammonium bis(O-phospho-L-serinate) trihydrate is described assuming a monoclinic supercell. Omission of weak superstructure reflections leads to a structure solution in an orthorhombic subcell.

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The structures of both known forms of the polymorphic material ortho-acetamidobenzamide have been determined by low-temperature neutron single-crystal diffraction.

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Seven isomeric N-(iodophenyl)nitrobenzamides all display different direction-specific intermolecular interactions and all form different three-dimensional framework structures.

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Fourfold twinning in the structure of 5-nitro-2,4-dihydro-1,2,4-triazol-3-one with Z′ = 4 arises from layer stacking faults.

short communications


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Using a new calculation scheme, reliable and physically meaningful values of the bond-valence parameters (r0 = 2.567 Å and b = 0.421 Å) have been deduced for the Bi3+/Br ion pair from the molecular geometry and from the crystal structure of BiBr3.
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